Systems and methods for processing ammonia

ABSTRACT

A method for ammonia decomposition is disclosed. The method may comprise providing a catalyst comprising an alumina support and a layer adjacent to the support. The layer comprises a perovskite phase comprising aluminum, cerium, and lanthanum, an oxide of at least one of an alkali metal and a rare earth metal, and an active metal. The method may comprise bringing the catalyst in contact with ammonia at a temperature of from about 400° C. to 700° C. to generate a reformate stream comprising hydrogen and nitrogen at an ammonia conversion efficiency of at least about 70%. The method may further comprise directing the hydrogen to a fuel cell to generate electricity. The method may further comprise generating heat for a reformer comprising the catalyst by combustion of gases or by electricity generated from hydrogen.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.63/418,249, filed Oct. 21, 2022, and U.S. Provisional Application No.63/427,286, filed Nov. 22, 2022, each of which is incorporated herein byreference in its entirety for all purposes.

BACKGROUND

Various systems may be operated using a fuel source. The fuel source mayhave a specific energy corresponding to an amount of energy stored orextractable per unit mass of fuel. The fuel source may be provided tothe various systems to enable such systems to generate energy and/ordeliver power (e.g., for movement or transportation purposes).

Ammonia is an attractive alternative energy fuel source, especiallybecause it does not contain carbon, and therefore does not emit carbonwhen used as a fuel. Ammonia can be burned in an internal combustionengine, although a supplemental fuel (e.g., hydrogen) is often necessaryto provide acceptable combustion characteristics. Ammonia can also beused as a hydrogen carrier, and it can undergo catalytic oxidation toyield nitrogen and hydrogen (which may then be used to power a fuelcell). However, many alternative fuels (including ammonia) have lowerenergy density or conversion efficiency than conventional fossil fuels,resulting in some reluctance of the markets to move to cleaner powerplants.

SUMMARY

Hydrogen can be leveraged as a clean energy source to power varioussystems. Hydrogen can provide a distinct advantage over other types offuel such as diesel, gasoline, or jet fuel, which have specific energiesof about 45 megajoules per kilogram (MJ/kg) (heat), or lithium-ionbatteries, which have a specific energy of about 0.95 MJ/kg(electrical). In contrast, hydrogen has a specific energy of over 140MJ/kg (heat). As such, 1 kg of hydrogen can provide the same amount ofenergy as about 3 kg of gasoline or kerosene. Thus, hydrogen as a fuelsource can help to reduce the amount of fuel (by mass) needed to providea comparable amount of energy as other traditional sources of fuel.Further, systems that use hydrogen as a fuel source (e.g., as acombustion reactant) generally produce benign or nontoxic byproductssuch as water while producing minimal or near zero harmful emissionssuch as carbon dioxide or nitrous oxide emissions, thereby reducing theenvironmental impacts of various systems (e.g., modes of transportation)that use hydrogen as a fuel source.

Recognized herein are various limitations with conventional catalystsused to extract hydrogen from ammonia (e.g., through an ammoniadecomposition process or reaction). Ammonia decomposition may also bereferred to as ammonia cracking, ammonia reforming, or ammoniadissociation. Ammonia decomposition can be a highly structure-dependentreaction, and the ability to control the morphology and/or the physicalor chemical properties of the active metal nanoparticles used todecompose ammonia molecules may be limited when using conventionalcatalyst fabrication methods. As such, more efficient use of activemetal nanoparticles is difficult, and conventional catalysts oftencomprise an increased active metal nanoparticle content. Further, thenanoparticles may not be highly dispersed, which can reduce theefficiency of the catalyst. Conventional catalysts may also exhibit lowheat transfer rates, which is undesirable for endothermic ammoniadecomposition reactions. Conventional catalysts may also lack stabilityat high temperatures, in the presence of impurities in industrial gradeammonia, or under mechanical perturbations, and may not be able towithstand harsh reaction conditions or maintain the necessary physicaland chemical properties needed to crack ammonia more efficiently. Someconventional catalysts may comprise bead, extrudate or pellet typecatalyst supports, but when catalyst materials are compressed into theseform factors, the inside materials of the pellet may not be fullyutilized, which can be wasteful and inefficient. As used herein, themorphology of the active metal nanoparticle support may correspond to asize, shape, aspect ratio, pore structure, pore size, pore shape, porevolume, pore density, pore size distribution, grain structure, grainsize, grain shape, crystal structure, flake size, or layered structureof the one or more active metal nanoparticles. As used herein, thephysical or chemical property of the active metal nanoparticles maycomprise a size, a size distribution, an aspect ratio, a facetdistribution, an Arrhenius acidity or basicity, a Lewis acidity orbasicity, or a hydrophilicity or hydrophobicity of the one or moreactive metal nanoparticles.

The present disclosure provides systems and methods for addressing atleast the abovementioned shortcomings noted for conventional catalysts.Some aspects of the present disclosure are directed to improved catalystmaterials, related systems and methods for fabricating such improvedcatalyst materials, and methods of using such improved catalystmaterials. The improved catalyst materials may exhibit an improvedmorphology and/or physical or chemical property for the active metalnanoparticles used to facilitate ammonia decomposition. The physical orchemical property may comprise a surface chemistry or property of theone or more active metal nanoparticles. The improved catalyst materialsmay also exhibit an improved level of dispersion of the active metalnanoparticles. The improved catalyst materials may further maintainfavorable physical and chemical properties under harsh reactionconditions, and may exhibit high thermal stability and improved heattransfer rates to enable efficient endothermic ammonia decompositionreactions.

The present disclosure further provides methods for fabricatingcatalysts comprising an improved material composition, active metalnanoparticle morphology, surface chemistry or property, and/orsupport-metal interactions. The fabrication methods disclosed herein maybe implemented to produce catalyst materials with high thermal stabilityand improved heat transfer characteristics. The catalyst materialsproduced using the methods of the present disclosure can be used todecompose ammonia efficiently at lower reaction temperatures for alonger duration, compared to conventional catalysts, and may extract agreater amount of hydrogen per unit weight or volume of ammonia whileusing a lower concentration of active metals (e.g., lower rutheniumcontents).

The present disclosure further provides one or more catalysts forprocessing ammonia. The one or more catalysts may comprise, for example,an improved pore structure and active metal nanoparticle morphologyand/or surface chemistry or property. The catalyst materials of thepresent disclosure may have high thermal stability and improved heattransfer characteristics. The catalyst materials may be used todecompose ammonia efficiently at lower reaction temperatures, and mayextract a greater amount of hydrogen per unit weight or volume ofammonia while using a lower concentration of active metals. In somecases, for the same amount of catalyst material used, more hydrogen maybe produced. In some cases, the hydrogen may be produced at lowerreaction temperatures.

In some aspects, the present disclosure relates to a method of ammoniadecomposition comprising: (a) providing a catalyst, comprising: asupport comprising alumina and a layer adjacent to the support, whereinthe layer comprises the support material doped with an oxide of at leastone of an alkali metal and a rare earth metal; wherein the layercomprises aluminum, cerium, and lanthanum; and one or more active metaladjacent to the layer, wherein the one or more active metal comprisesRu, Pt, or Pd; and wherein the concentration of the active metal is atleast about 0.1, and not more than about 15 wt %; and (b) bringing thecatalyst in contact with ammonia at a temperature of at least about 400°C. and not more than about 700° C. to generate a reformate streamcomprising hydrogen and nitrogen at an ammonia conversion efficiency ofat least about 70% and at most about 99.9%.

In some instances, the catalyst comprises a layer comprising thetaalumina (θ-alumina) or gamma alumina (γ-alumina).

In some instances, the catalyst comprises a layer comprising La at aconcentration of at least about 1 and not more than about 20 mol % withrespect to the layer and support.

In some cases, the catalyst comprises a molar ratio of La and Cecomprising at least about 50:50 and not more than about 90:10.

In some cases, the alkali metal comprises K or Cs, and the catalystcomprises a layer comprising a molar ratio of K or Cs to the one or moreactive metal comprising at least about 1:2 and not more than about 6:1.

In some instances, the active metal comprises Ru, the catalyst comprisesa concentration of Ru comprising at least about 0.5 wt % and not morethan about 5 wt %, with respect to the weight of the catalyst.

In some cases, the method comprises bringing ammonia in contact with thecatalyst of the present disclosure at a space velocity of at least about1 and not more than about 100 liters of ammonia per hour per gram ofcatalyst.

In some instances, the method comprises generating electricity byproviding hydrogen produced by the catalyst of the present disclosure toat least one fuel cell, wherein the at least one fuel cell comprises aProton Exchange Membrane Fuel Cell (PEMFC), a Solid Oxide Fuel Cell(SOFC), a Molten Carbonate Fuel Cell (MCFC), an Alkaline Fuel Cell(AFC), an Alkaline Membrane Fuel Cell (AMFC), or a Phosphoric Acid FuelCell (PAFC).

In some instances, the method comprises contacting the catalyst of thepresent disclosure with ammonia to generate the reformate stream is anauto-thermal reforming process so that at least part of the reformatestream provides heat for the auto-thermal reforming process.

In some cases, the at least part of the reformate stream is at least oneof: (1) combusted to generate the heat, or (2) converted byhydrogen-to-electricity conversion to generate the heat, therebyproviding the heat for the auto-thermal reforming process.

In some instances, undecomposed ammonia in the reformate stream isremoved by an ammonia filter, wherein the ammonia filter comprises anadsorbent, a membrane separation module, or an ammonia scrubber.

In some instances, a pressure swing adsorption (PSA) module is used toremove nitrogen from the reformate stream.

In some cases, (b) comprises directing the ammonia to a first reformerto generate the reformate stream; wherein the method comprisescombusting the reformate stream in a combustion heater to heat a secondreformer; and directing additional ammonia to the second reformer togenerate additional hydrogen for the reformate stream, wherein a firstportion of the reformate stream is combusted to heat the secondreformer.

In some instances, the first reformer is heated using at least one of anelectrical heater or combustion of the reformate stream.

In some cases, (b) comprises directing the ammonia to a reformer at anammonia flow rate to generate the reformate stream, wherein the methodfurther comprises: combusting a first portion of the reformate streamwith oxygen at an oxygen flow rate in a combustion heater to heat thereformer; and processing a second portion of the reformate stream in ahydrogen processing module; and based at least in part on a stimulus,performing one or more of: (i) changing the ammonia flow rate; (ii)changing a percentage of the reformate stream that is the first portionof the reformate stream; (iii) changing a percentage of the reformatestream that is the second portion of the reformate stream; or (iv)changing the oxygen flow rate.

In some instances, the stimulus comprises: (x) a change in an amount ofthe hydrogen used by the hydrogen processing module; (y) a temperatureof the reformer being outside of a target temperature range; or (z) achange in an amount or concentration of ammonia in the reformate stream.

In some cases, the change in an amount of the hydrogen used by thehydrogen processing module is a projected change in the amount of thehydrogen used by the hydrogen processing module.

In some instances, the hydrogen processing module comprises a fuel celland the fuel cell provides an anode off-gas comprising hydrogen to thecombustion heater.

In some cases, (b) comprises directing the ammonia to a reformer at anammonia flow rate to generate the reformate stream, wherein the methodfurther comprises: combusting a first portion of the reformate streamwith oxygen at an oxygen flow rate in a combustion heater to heat thereformer; processing a second portion of the reformate stream in ahydrogen processing module; measuring a temperature in the reformer orthe combustion heater; and based at least in part on the measuredtemperature being outside of a target temperature range of the reformeror the combustion heater, performing one or more of: (i) changing theammonia flow rate; (ii) changing the oxygen flow rate; (iii) changing apercentage of the reformate stream that is the second portion of thereformate stream; (iv) changing a percentage of the reformate streamthat is the first portion of the reformate stream; or (v) changing apercentage of the reformate stream that is directed out of thecombustion heater.

In some instances, the hydrogen processing module comprises a fuel celland the fuel cell provides an anode off-gas comprising hydrogen to thecombustion heater.

Additional aspects and advantages of the present disclosure will becomereadily apparent to those skilled in this art from the followingdetailed description, wherein only illustrative embodiments of thepresent disclosure are shown and described. As will be realized, thepresent disclosure is capable of other and different embodiments, andits several details are capable of modifications in various obviousrespects, all without departing from the disclosure. Accordingly, thedrawings and descriptions are to be regarded as illustrative in nature,and not as restrictive.

INCORPORATION BY REFERENCE

All publications, patents, and patent applications mentioned in thisspecification are herein incorporated by reference to the same extent asif each individual publication, patent, or patent application wasspecifically and individually indicated to be incorporated by reference.To the extent publications and patents or patent applicationsincorporated by reference contradict the disclosure contained in thespecification, the specification is intended to supersede and/or takeprecedence over any such contradictory material.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features of the invention are set forth with particularity inthe appended claims. A better understanding of the features andadvantages of the present invention will be obtained by reference to thefollowing detailed description that sets forth illustrative embodiments,in which the principles of the invention are utilized, and theaccompanying drawings (also “Figure” and “FIG.” herein), of which:

FIG. 1 schematically illustrates an example system for processingammonia to generate hydrogen fuel, in accordance with some embodiments.

FIG. 2 schematically illustrates an example method of hydrogen storageusing liquid chemicals, in accordance with some embodiments.

FIG. 3 schematically illustrates an example hydrogen extraction reformercomprising a heterogeneous catalyst, in accordance with someembodiments.

FIG. 4 schematically illustrates an example process for modifying andenhancing a catalyst support, in accordance with some embodiments.

FIG. 5 schematically illustrates an example process for processing aprecursor material, in accordance with some embodiments.

FIG. 6A schematically illustrates the effects of reducing a catalyst onammonia conversion efficiency, in accordance with some embodiments.

FIG. 6B schematically illustrates the effects of thermally treating acatalyst on hydrogen generation or production rates, in accordance withsome embodiments.

FIG. 6C schematically illustrates the effects of active metal promotionof a catalyst on ammonia conversion efficiency, in accordance with someembodiments.

FIG. 6D schematically illustrates the effects of doping catalysts onammonia conversion efficiency, in accordance with some embodiments.

FIG. 6E schematically illustrates the effects of doping catalysts onammonia conversion efficiency, in accordance with some embodiments.

FIG. 7 schematically illustrates a computer system that is programmed orotherwise configured to implement methods provided herein.

FIG. 8 illustrates a comparison of ammonia conversion efficiencies usingvarious catalysts synthesized using different size alumina carriers, inaccordance with some embodiments.

FIG. 9 illustrates a comparison of ammonia conversion efficiencies forvarious catalysts synthesized via reduction at different temperatures,in accordance with some embodiments.

FIG. 10 illustrates a comparison of ammonia conversion efficiencies forvarious catalysts synthesized using different gamma- and theta-aluminasupports, in accordance with some embodiments.

FIG. 11 illustrates a comparison of ammonia conversion efficiencies forvarious catalysts synthesized using different ruthenium precursors, inaccordance with some embodiments.

FIG. 12 illustrates a comparison of ammonia conversion efficiencies forvarious example catalysts fabricated using different combinations ofmaterials and production methods, in accordance with some embodiments.

FIG. 13 illustrates a comparison of ammonia conversion efficiencies forvarious catalysts synthesized with different La and Ce ratios, inaccordance with some embodiments.

FIG. 14 illustrates a comparison of ammonia conversion efficiencies forvarious catalysts having different La:Ce molar ratios and variations inammonia conversion efficiencies based on changes in Ce content, inaccordance with some embodiments.

FIG. 15 illustrates a comparison of ammonia conversion efficiencies forvarious catalysts having different La:Ce molar ratios and variations inammonia conversion efficiencies based on different operatingtemperatures, in accordance with some embodiments.

FIG. 16 is block diagram illustrating an ammonia reforming system, inaccordance with some embodiments.

DETAILED DESCRIPTION

While various embodiments of the invention have been shown and describedherein, it will be obvious to those skilled in the art that suchembodiments are provided by way of example only. Numerous variations,changes, and substitutions may occur to those skilled in the art withoutdeparting from the invention. It should be understood that variousalternatives to the embodiments of the invention described herein may beemployed. It should be understood that any of the embodiments,configurations and/or components described with respect to a particularfigure may be combined with other embodiments, configurations, and/orcomponents described with respect to other figures.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of exampleembodiments. As used herein, the singular forms “a,” “an” and “the” areintended to include the plural forms as well (and vice versa), unlessthe context clearly indicates otherwise. For example, “a,” “an,” and“the” may be construed as “one or more.”

The present disclosure may be divided into sections using headings. Theheadings should not be construed to limit the present disclosure, andare merely present for organization and clarity purposes.

Whenever the term “at least”, “at least about”, “greater than”, “greaterthan about”, “greater than or equal to”, or “greater than or equal toabout” precedes the first numerical value in a series of two or morenumerical values, the term “at least”, “at least about”, “greater than”,“greater than about”, “greater than or equal to”, or “greater than orequal to about” applies to each of the numerical values in that seriesof numerical values. For example, greater than or equal to about 1, 2,or 3 is equivalent to greater than or equal to about 1, greater than orequal to about 2, or greater than or equal to about 3.

Whenever the term “no more than”, “no more than about”, “not more than”,“not more than about”, “less than”, “less than about”, “less than orequal to”, or “less than or equal to about” precedes the first numericalvalue in a series of two or more numerical values, the term “no morethan”, “no more than about”, “not more than”, “not more than about”,“less than”, “less than about”, “less than or equal to”, or “less thanor equal to about” applies to each of the numerical values in thatseries of numerical values. For example, less than or equal to about 3,2, or 1 is equivalent to less than or equal to about 3, less than orequal to about 2, or less than or equal to about 1.

The terms “at least one of” and “one or more of” may be usedinterchangeably. The expressions “at least one of A and B” and “at leastone of A or B” may be construed to mean at least A, at least B, or atleast A and B (i.e., a set comprising A and B, which set may include oneor more additional elements). The term “A and/or B” may be construed tomean only A, only B, or both A and B.

The expressions “at least about A, B, and C” and “at least about A, B,or C” may be construed to mean at least about A, at least about B, or atleast about C. The expressions “at most about A, B, and C” and “at mostabout A, B, or C” may be construed to mean at most about A, at mostabout B, or at most about C.

The expression “between about A and B, C and D, and E and F” may beconstrued to mean between about A and about B, between about C and aboutD, and between about E and about F. The expression “between about A andB, C and D, or E and F” may be construed to mean between about A andabout B, between about C and about D, or between about E and about F.

The expression “about A to B and C to D” may be construed to meanbetween about A and about B and between about C and about D. Theexpression “about A to B or C to D” may be construed to mean betweenabout A and about B or between about C and about D.

The terms “decompose”, “dissociate”, “reform”, “crack”, “react”,“convert”, “dehydrogenate”, “extract”, “strip”, and “break down,” andtheir grammatical variations, may be construed interchangeably. Forexample, the expression “decomposition of ammonia” may beinterchangeable with “dissociation of ammonia,” “reforming of ammonia,”“cracking of ammonia,” “conversion of ammonia,” etc.

The terms “reformer”, “reactor”, “cracker”, “breaker”, “decomposer”,“dissociator”, “converter”, “dehydrogenator”, “extractor” and “stripper”may be construed interchangeably. For example, the expression “thecatalyst in the reformer” may be interchangeable with “the catalyst inthe reactor”, “the catalyst in the cracker”, “the catalyst in thedehydrogenator”, etc.

The terms “ammonia conversion” and “ammonia conversion efficiency,” andtheir grammatical variations, may be construed as a fraction of ammoniathat is converted to hydrogen and nitrogen, and may be construedinterchangeably. For example, “ammonia conversion” or “ammoniaconversion efficiency” of 90% may represent 90% of ammonia beingconverted to hydrogen and nitrogen.

The term “turnover frequency” may be construed as the forward reactionrate of ammonia decomposition, measured either as ammonia consumption orhydrogen production normalized per unit catalyst per unit time(Amount_(ammonia or hydrogen) Amount_(cat) ⁻¹ time⁻¹).Amount_(ammonia or hydrogen) may be measured asmmol_(ammonia or hydrogen), mol_(ammonia or hydrogen),g_(ammonia or hydrogen), or mL_(ammonia or hydrogen). Amount_(cat) ⁻ maybe measured as g_(cat), g_(active metal), g_(surface active metal),g_(active sites), mol_(cat), mol_(active metal),mol_(surface active metal), or mol_(active sites). Time may be measuredas seconds, minutes, hours or days.

In some cases, the term “turnover frequency” may be construed as the netreaction rate of ammonia decomposition (i.e., forward reaction minusreverse reaction), measured either as ammonia consumption or hydrogenproduction normalized per unit catalyst per unit time(Amount_(ammonia or hydrogen) Amount_(cat) ⁻¹ time⁻¹).Amount_(ammonia or hydrogen) may be measured asmmol_(ammonia or hydrogen), mol_(ammonia or hydrogen),g_(ammonia or hydrogen), or mL_(ammonia or hydrogen). Amount_(cat) ⁻ maybe measured as g_(cat), g_(active metal), g_(surface active metal),g_(active sites), mol_(cat), mol_(active metal),mol_(surface active metal), or mol_(active sites). Time may be measuredas seconds, minutes, hours or days.

The terms “production rate” and “consumption rate” may be construed asthe production or consumption of a compound involved in the reaction,measured as a net rate=forward reaction−reverse reaction. The unit for“production rate” and “consumption rate” may beAmount_(ammonia or hydrogen) Amount_(cat) ⁻¹ time⁻¹.Amount_(ammonia or hydrogen) may be measured asmmol_(ammonia or hydrogen), mol_(ammonia or hydrogen),g_(ammonia or hydrogen), or mL_(ammonia or hydrogen). Amount_(cat) ⁻ maybe measured as g_(cat), g_(active metal), g_(surface active metal),g_(active sites), mol_(cat), mol_(active metal),mol_(surface active metal), or mol_(active sites). Time may be measuredas seconds, minutes, hours or days.

The term “space velocity” may be defined as the volumetric flow rate ofthe feed gas (e.g. ammonia) relative to the mass of the catalystmaterial, and may be expressed in units of liters (or milliliters) perhour of gas per gram of catalyst, e.g., L hr⁻¹ g⁻¹, L_(gas) hr⁻¹ g_(cat)⁻¹, L_(NH3) hr⁻¹ g_(cat) ⁻¹, L_(ammonia) hr⁻¹ g_(cat) ⁻¹, mL hr⁻¹ g⁻¹,mL_(gas) hr⁻¹ g_(cat) ⁻¹, mL_(NH3) hr⁻¹ g_(cat) ⁻¹, or mL_(ammonia) hr⁻¹g_(cat) ⁻¹.

The term “auto-thermal reforming” may be construed as a condition wherean ammonia decomposition reaction (2NH₃→N₂+3H₂; an endothermic reaction)is heated by a hydrogen combustion reaction (2H₂+O₂→2H₂O; an exothermicreaction) using at least part of the hydrogen produced by the ammoniadecomposition reaction itself.

In some cases, the term “auto-thermal reforming” may be construed as acondition where an ammonia decomposition reaction is heated by ahydrogen combustion reaction using at least part of hydrogen produced bythe ammonia decomposition reaction itself, electrical heating, or acombination of both (which may result in an overall positive electricaland/or chemical energy output). For example, if “auto-thermal reforming”is performed using a hydrogen combustion reaction and/or electricalheating, the hydrogen produced from the ammonia decomposition reactionmay be enough to provide the hydrogen combustion reaction withcombustion fuel, and/or to provide electrical energy for the electricalheating via hydrogen-to-electricity conversion devices (e.g., fuel cell,combustion engine, etc.).

In some cases, the hydrogen provided for the hydrogen combustionreaction and/or the electrical heating may or may not use the hydrogenfrom the ammonia decomposition reaction (for example, the hydrogen maybe provided by a separate hydrogen source, the electricity may beprovided from batteries or a grid, etc.).

In some cases, “auto-thermal reforming” may be construed as a conditionwhere an ammonia decomposition reaction is heated by a combustionreaction (e.g., ammonia combustion, hydrocarbon combustion, etc.),electrical heating, or a combination of both, which may result in anoverall positive electrical and/or chemical energy output. For example,if “auto-thermal reforming” is performed using a combustion reactionand/or electrical heating, the chemical energy (e.g., lower heatingvalue) from the hydrogen produced from the ammonia decompositionreaction may be higher than the combustion fuel chemical energy (e.g.,lower heating value), and/or may be enough to provide electrical energyfor the electrical heating via hydrogen-to-electricity conversiondevices (e.g., fuel cell, combustion engine, etc.).

The examples described herein are provided as embodiments to demonstratethe effectiveness of the disclosed catalyst compositions and methods offabrication. Each of these catalysts were prepared according to thedetailed preparation methods described herein.

In one aspect, the present disclosure provides a method of fabricating acatalyst for ammonia processing or decomposition, comprising: (a)providing a catalyst support; (b) thermally, chemically, physically, orelectrochemically processing the catalyst support to alter a porecharacteristic of the catalyst support; (c) depositing a compositesupport material on the catalyst support, wherein the composite supportmaterial comprises a morphology or a surface chemistry or property; and(d) depositing one or more active metals on at least one of thecomposite support material and the catalyst support, wherein the one ormore active metals comprise one or more nanoparticles configured toconform to the morphology or the surface chemistry or property of thecomposite support material when subjected to a thermal or chemicaltreatment, thereby improving one or more active sites on thenanoparticles for ammonia processing or decomposition.

In some cases, the morphology comprises a pore structure, a pore size, apore shape, a pore volume, a pore density, a pore size distribution, agrain structure, a grain size, a grain shape, a crystal structure, aflake size, or a layered structure. In some instances, the surfacechemistry or property comprises an elemental composition, an Arrheniusacidity or basicity, a Lewis acidity or basicity, a surface hydroxylgroup density, or a hydrophilicity or hydrophobicity. In some cases,thermally, chemically, physically, or electrochemically processing thecatalyst support comprises subjecting the catalyst support to one ormore thermal, chemical, physical, or electrochemical processes ortreatments to improve one or more pores or a surface chemistry orproperty of the catalyst support. In some instances, improving the oneor more pores comprises (i) modifying a size of the one or more pores,(ii) modifying a pore volume of the catalyst support, (iii) modifyingthe pore size distribution or (iv) modifying a pore density of thecatalyst support. In some cases, improving the surface chemistry orproperty comprises modifying (i) an Arrhenius acidity or basicity, (ii)a Lewis acidity or basicity, (iii) a surface hydroxyl group density, or(iv) a surface hydrophilicity or hydrophobicity.

In some cases, the composite support material is deposited usingphysical vapor deposition or chemical vapor deposition. In someinstances, the morphology or the surface chemistry or property of thecomposite support material conforms to a morphology or a surfacechemistry or property of the catalyst support. In some cases, the one ormore active metals are deposited using physical vapor deposition orchemical vapor deposition. In some instances, the method may furthercomprise thermally or chemically activating the one or more activemetals. In some cases, thermally, physically, chemically, orelectrochemically activating the one or more active metals induces agrowth of one or more nanoparticles of the active metals. In someinstances, the one or more nanoparticles are configured to grow whileconforming to the morphology or the surface chemistry or property of thecomposite support material when thermally, physically,electrochemically, or chemically activated. In some cases, the methodmay further comprise combining the catalyst with one or more promotersto modify or improve a morphology, an active site, an electron density,an Arrhenius acidity or basicity, a Lewis acidity or basicity, or anelectron state of the catalyst.

In some embodiments, the one or more promoters comprise sodium (Na),potassium (K), rubidium (Rb), cesium (Cs), magnesium (Mg), calcium (Ca),strontium (Sr), or barium (Ba). In some embodiments, the one or moreactive metals comprise ruthenium (Ru), nickel (Ni), rhodium (Rh),iridium (Ir), cobalt (Co), molybdenum (Mo), iron (Fe), platinum (Pt),chromium (Cr), palladium (Pd), or copper (Cu). In some embodiments, thecatalyst support comprises aluminum oxide (Al₂O₃), magnesium oxide(MgO), cerium dioxide (CeO₂), silicon dioxide (SiO₂), yttrium oxide(Y₂O₃), zirconium oxide (ZrO₂), one or more zeolites, titanium dioxide(TiO₂), lanthanum oxide (La₂O₃), chromium oxide (Cr₂O₃), or calciumoxide (CaO). In some cases, the composite support material comprises acarbon-based material, a boron-based material, or a metal oxide. In someinstances, the carbon-based material comprises graphite, activatedcarbon (AC), one or more carbon nanotubes (CNT), one or more carbonnanofibers (CNF), graphene oxide (GO), one or more carbon nanoribbons,or reduced graphene oxide (rGO). In some cases, the boron-based materialcomprises hexagonal boron nitride (hBN), boron nitride nanotubes (BNNT),or boron nitride nanosheets (BNNS). In some instances, the metal oxidecomprises aluminum oxide (Al₂O₃), titanium dioxide (TiO₂), magnesiumoxide (MgO), lanthanum oxide (La₂O₃), cerium dioxide (CeO₂), yttriumoxide (Y₂O₃), one or more CeO₂ nanotubes, nanorods or nanocubes,mesoporous silica, zirconium dioxide (ZrO₂), chromium oxide (Cr₂O₃), orcalcium oxide (CaO). In some cases, the composite support material mayinclude yttria-stabilized zirconia (YSZ), hydrotalcite (Mg₂Al-LDO), ametal organic framework (MOF) (e.g., MIL-101), a zeolitic imidazolateframework (ZIF), an alkaline amide (NaNH₂, Ca(NH₂)₂, Mg(NH₂)₂), aninorganic electride (e.g., Cl₂A7:e-), Halloysite nanotubes (HNT), ABO3Perovskite, AB2O4 Spinel, a mesoporous silicate (e.g., MCM-41), or anycombination thereof.

In some embodiments, the method may further comprise thermally,physically, chemically or electrochemically treating a surface of thecatalyst support material to improve a pore structure or a surfacechemistry or property of the catalyst support material. In some cases,the one or more ammonia molecules are configured to bind or attach tothe one or more active sites on the active metals for decomposition ofthe one or more ammonia molecules. In some instances, the positions,orientations, and/or density of the one or more active sites aredetermined based at least in part on the morphology and/or surfacechemistry or property. In some cases, the catalyst support comprises abead, a pellet, a powder, a thin film, a monolith, a foam, a reformerwall, a heating element, one or more wires, a mesh, engineered orcorrugated sheet, or a porous solid material form factor. In someinstances, the pore characteristic comprises a pore structure, a poresize, a pore size distribution, a pore shape, a pore volume, or a poredensity. In some cases, the method may comprise altering a pore densityof the catalyst support. In some instances, the method may compriseincreasing the pore density of the catalyst support.

In another embodiment, the present disclosure provides a catalyst forammonia processing, comprising: a catalyst support comprising one ormore modified pore characteristics generated by thermal, physical,chemical, or electrochemical processing of the catalyst support; acomposite support material provided on the catalyst support, wherein thecomposite support material comprises a morphology or a surface chemistryor property; and one or more active metals provided on or embedded in atleast one of the composite support material and the catalyst support,wherein the one or more active metals comprise one or more nanoparticlesconfigured to conform to the morphology or the surface chemistry orproperty of the composite support material when thermally, physically,chemically or electrochemically activated, thereby improving one or moreactive sites on the nanoparticles for ammonia processing ordecomposition.

In some cases, the composite support material is deposited usingphysical vapor deposition or chemical vapor deposition. In someinstances, the morphology or the surface chemistry or property of thecomposite support material conforms to a morphology or a surfacechemistry or property of the catalyst support. In some cases, the one ormore active metals are deposited using physical vapor deposition orchemical vapor deposition. In some instances, the one or more activemetals are configured to conform to the morphology or the surfacechemistry or property of the composite support material when thermallyor chemically activated. In some cases, the one or more active metalsare configured to grow when thermally, physically, chemically, orelectrochemically activated. In some instances, the one or morenanoparticles are configured to grow while conforming to the morphologyor the surface chemistry or property of the composite support material.

In some instances, the morphology or the surface chemistry or propertyis generated or improved by thermally, physically, chemically, orelectrochemically treating a surface of the catalyst support material.In some cases, the one or more active metal nanoparticles comprise oneor more active sites to which one or more ammonia molecules areconfigured to attach or bind for decomposition of the one or moreammonia molecules. In some instances, the positions, orientations, ordensity of the one or more active sites are determined based at least inpart on the morphology or surface chemistry or property. In someinstances, the catalyst support comprises a bead, a pellet, a powder, athin film, a monolith, a foam, reformer wall, heating element, wires,mesh, engineered or corrugated sheet, or a porous solid material formfactor.

Reformer

In an aspect, the present disclosure provides a system for processing asource material. The system may comprise one or more reformers. The oneor more reformers may comprise one or more catalysts. The one or morecatalysts may be used to process a source material. The one or morecatalysts may be improved to enhance the processing of the sourcematerial. The source material may comprise, for example, ammonia (NH₃).The source material may be processed to generate a fuel source. The fuelsource may comprise, for example, hydrogen and/or nitrogen. The fuelsource may be provided to one or more hydrogen fuel cells, which may beconfigured to use the fuel source to generate electrical energy. Suchelectrical energy may be used to power various systems, vehicles, and/ordevices.

FIG. 1 schematically illustrates a block diagram of an example methodfor processing a source material to produce electrical energy. A sourcematerial 110 may be provided to a reformer 120. The source material 110may comprise a compound comprising one or more hydrogen molecules. Thecompound may be, for example, ammonia or NH₃. In some cases, thecompound may comprise a hydrocarbon C_(x)H_(y). The source material 110may be provided to a reformer 120. The source material 110 may be in agaseous state and/or a liquid state. The reformer 120 may be designed orconfigured to process the source material 110 using one or morecatalysts 121 to extract, produce, or release a fuel source 130 from thesource material 110. In some cases, processing the source material 110may comprise heating the one or more catalysts 121 to extract, produce,or release the fuel source 130 from the source material 110. The fuelsource 130 may comprise, but may not be limited to, hydrogen and/ornitrogen. The fuel source 130 may be provided to one or more fuel cellsor one or more combustion engines for the generation of electricalenergy or mechanical work. Such electrical energy may be used to powervarious system, vehicles, and/or devices, including, for example,terrestrial, aerial, or aquatic vehicles.

In some cases, the fuel source 130 may be provided to various chemicalor industrial processes, including, but not limited to, steel or ironprocessing, combustion engines, combustion turbines, hydrogen storage,hydrogen for chemical processes, hydrogen fueling stations, etc. In somecases, the fuel source 130 can be supplied as a pilot, auxiliary, ormain fuel to the combustion engines or combustion turbines.

As described above, one or more fuel cells may be used to generateelectrical energy from the fuel source 130, which may comprise, but maynot be limited to, hydrogen and/or nitrogen. In some cases, the one ormore fuel cells may generate electricity through an electrochemicalreaction between fuels. The fuels may comprise the hydrogen and/or thenitrogen in the fuel source 130. The electricity generated by the fuelcells may be used to power one or more systems, vehicles, or devices. Insome cases, excess electricity generated by the fuel cells may be storedin one or more energy storage units (e.g., batteries) for future use. Insome instances, the fuel cells may be provided as part of a larger fuelcell system. The fuel cell system may comprise an electrolysis module.Electrolysis of a byproduct of the one or more fuel cells (e.g., water)may allow the byproduct to be removed, through decomposition of thebyproduct into one or more constituent elements (e.g., oxygen and/orhydrogen). Electrolysis of the byproduct can also generate additionalfuel (e.g., hydrogen) for the fuel cell.

As described above, one or more combustion engines may be used togenerate electrical energy or mechanical work from the fuel source 130,which may comprise, but may not be limited to, hydrogen and/or nitrogen.In some cases, the one or more combustion engines may generatemechanical work through combustion of one or more fuels. The mechanicalwork can be converted to electrical energy by one or more electricalgenerators. The fuels may comprise the hydrogen and/or the nitrogen inthe fuel source 130. The electricity or mechanical work generated by thecombustion engines may be used to power one or more systems, vehicles,or devices. In some cases, excess electricity or mechanical workgenerated by the combustion engines may be stored in one or more energystorage units (e.g., batteries) for future use. In some instances, thecombustion engine may be provided as part of a larger engine or powergeneration system. The combustion engine system may comprise acombustion chamber. Electrolysis of a byproduct of the one or morecombustion engines (e.g., water) may allow the byproduct to be removed,for example, through decomposition of the byproduct into one or moreconstituent elements (e.g., oxygen and/or hydrogen). Electrolysis of thebyproduct can also generate additional fuel (e.g., hydrogen) for thecombustion engine.

FIG. 2 schematically illustrates an example method of hydrogen storageusing liquid chemicals, in accordance with some embodiments. Hydrogen,whether produced by electrolysis of renewables or through hydrocarbonreforming, may be stored using one or more liquid chemicals. In somecases, the one or more liquid chemicals may comprise, for example,ammonia, a liquid organic hydrogen carrier (LOHC), formic acid (HCOOH),or methanol (CH₃OH). The hydrogen may be stored in a hydrogen-rich formor a hydrogen-lean form. The one or more liquid chemicals comprising thehydrogen may be processed as described herein to release the hydrogenstored in the liquid chemicals. Once released, the hydrogen may be usedfor power generation (e.g., stationary or portable power generation), ormay be provided to a hydrogen storage, hydrogen fueling station, orhydrogen fueling site.

In some cases, ammonia may be used as a hydrogen carrier. A hydrogencarrier may comprise a fluid or liquid chemical that can be used tostore hydrogen. The use of ammonia as an energy carrier provides thebenefits of hydrogen fuel (e.g., carbon-free and high volumetric energydensity) once the ammonia is broken down into hydrogen, while takingadvantage of (a) ammonia's greater volumetric density compared to bothgaseous and liquid hydrogen and (b) the ability to transport ammonia atstandard temperatures and pressures without requiring complex and highlypressurized storage vessels like those typically used for storing andtransporting hydrogen.

In some cases, hydrogenation may be used to store the hydrogen in one ormore fluids or liquid chemicals (e.g., ammonia). Hydrogenation may referto the treatment of materials or substances with molecular hydrogen (H₂)to add one or more pairs of hydrogen atoms to various constituentcompounds (e.g., one or more unsaturated compounds) making up thematerials or substances. Hydrogenation may be performed using acatalyst, which can allow the reaction to occur under normal conditionsof temperature and/or pressure. In some cases, the Haber-Bosch process(an artificial nitrogen fixation process) may be used to produceammonia. The process may be used to convert atmospheric nitrogen (N₂) toammonia (NH₃) by a reaction with hydrogen (e.g., H₂ produced or obtainedby electrolysis) using a metal catalyst under various reactiontemperatures and pressures:

As described above, the Haber-Bosch process may be used to produceammonia, which can be used as a hydrogen carrier. Using ammonia as ahydrogen carrier may provide several benefits, including easy storage atrelatively standard conditions (0.8 MPa, 20° C. in liquid form), andconvenient transportation. Ammonia also has a relatively high hydrogencontent (17.7 wt %, 120 grams of H₂ per liter of liquid ammonia).Further, the production of ammonia using the Haber-Bosch process can bepowered by renewable energy sources (e.g., solar photovoltaic orsolar-thermal), which makes the production process environmentally safeand friendly, as N₂ is the only byproduct and there is no furtheremission of CO₂. Once the ammonia is produced, it may be processed(e.g., decomposed using a catalyst) to release the hydrogen through adehydrogenation process. The released hydrogen may then be provided toone or more fuel cells, such as a proton-exchange membrane fuel cell(PEMFC) having a proton-conducting polymer electrolyte membrane, apolymer electrolyte membrane (PEM) fuel cell, a solid-oxide fuel cell(SOFC), or one or more combustion engines having one or more combustionchambers. PEMFCs may have relatively low operating temperatures and/orpressure ranges (e.g., from about 50 to 100° C.). A proton exchangemembrane fuel cell can be used to transform the chemical energyliberated during the electrochemical reaction of hydrogen and oxygeninto electrical energy, as opposed to the direct combustion of hydrogenand oxygen gases to produce thermal energy. PEMFCs can generateelectricity and operate on the opposite principle to PEM electrolysis,which consumes electricity. Combustion engines can generate mechanicalwork or electricity via combustion of (i) hydrogen and oxygen gases or(ii) hydrogen, ammonia, and oxygen gases. The methods and systemsdisclosed herein may be implemented to achieve thermally efficienthydrogen production, and may be scaled for application to high energydensity power systems.

FIG. 3 schematically illustrates a hydrogen extraction reformer 300 forextracting hydrogen from ammonia. The extraction of hydrogen fromammonia may be accomplished using one or more catalysts 340. The one ormore catalysts 340 may comprise a heterogenous catalyst. A heterogenouscatalyst may comprise a catalyst having a different phase than that ofthe reactants 310 (e.g., NH₃) or products 320 and/or 330 (N₂ and/or H₂).The one or more catalysts 340 may comprise a plurality of metalnanoparticles 350 embedded in, on, or within a support material 360(e.g., a composite support and/or a catalyst support as describedherein). The impregnation of the metal nanoparticles 350 into, onto, orwithin the support materials 360 may lower an activation energy barrierof the ammonia decomposition reaction, thereby allowing the one or morecatalysts 340 to efficiently crack or decompose ammonia at lowerreaction temperatures.

Metal Foam Catalysts

In some embodiments, the catalysts may comprise one or more metal foamcatalysts. The one or more catalysts may comprise, for example, amodified metal foam catalyst. The catalyst materials may be subjected toor may undergo one or more enhancements and/or treatments as shown anddescribed herein. In some cases, the catalyst may comprise a nickelchromium aluminum (NiCrAl) foam.

In some cases, at least one of the first catalyst and the secondcatalyst may comprise a metal foam catalyst. The metal foam catalyst maycomprise nickel, iron, chromium, and/or aluminum. In some cases, themetal foam catalyst may comprise one or more alloys comprising nickel,iron, chromium, and/or aluminum.

In some cases, the metal foam catalysts may comprise a catalytic coatingof one or more powder or pellet catalysts. The catalytic coating maycomprise a metal material, a promoter material, and/or a supportmaterial. The metal material may comprise, for example, ruthenium,nickel, rhodium, iridium, cobalt, molybdenum, iron, platinum, chromium,palladium, and/or copper. The promoter material may comprise, forexample, sodium, potassium, rubidium, and/or cesium. In some cases, thesupport material may comprise, for example, at least one of Al₂O₃, MgO,CeO₂, SiO₂, TiO₂, Y₂O₃, ZrO₂, SiC, silicon nitride (SiN), MgAl₂O₄,CaAl₂O₄, CoAl₂O₄, hexagonal boron nitride, one or more boron nitridenanotubes, and/or one or more carbon nanotubes. In some cases, thesupport material may comprise at least one of Al_(x)O_(y), Mg_(x)O_(y),Ce_(x)O_(y), Si_(x)O_(y), Ti_(x)O_(y), Y_(x)O_(y), Zr_(x)O_(y),B_(x)N_(y), Si_(x)C_(y), Si_(x)N_(y), and/or C. In some embodiments, thecatalytic coating may comprise one or more ruthenium-based precursors.The one or more ruthenium-based precursors may comprise, for example,RuCl₃, Ru(NO)(NO₃)₃, or Ru₃(CO)₁₂. In any of the cases described herein,the metal foam catalyst may have an apparent electrical resistivity ofat least about 8 micro ohm-meters (μΩm).

In some cases, the metal foam catalyst may be processed using one ormore etching, alloying, leaching, or acidic treatments to enhance asurface area of the metal foam catalyst. In some cases, the metal foamcatalyst may be heat treated. In some cases, the metal foam catalyst maybe coated using a physical vapor deposition (PVD) treatment and/or achemical vapor deposition (CVD) treatment.

Catalysts Based on a Modified Support

In some embodiments, the one or more ammonia decomposition catalysts maycomprise a metal material, a promoter material, and/or a supportmaterial. In some cases, the metal material may comprise, for example,at least one of ruthenium, nickel, rhodium, iridium, cobalt, molybdenum,iron, platinum, chromium, palladium, and/or copper. In some cases, thepromoter material may comprise, for example, at least one of sodium,potassium, rubidium, cesium, magnesium, calcium, strontium, and/orbarium. In some cases, the support material may comprise at least one ofAl_(x)O_(y), Mg_(x)O_(y), Ce_(x)O_(y), Si_(x)O_(y), Ti_(x)O_(y),Y_(x)O_(y), Zr_(x)O_(y), B_(x)N_(y), Si_(x)C_(y), Si_(x)N_(y), and/or C.In some cases, the support material may comprise, for example, at leastone of Al₂O₃, MgO, CeO₂, SiO₂, SiC, TiO₂, Y₂O₃, ZrO₂, SiN, MgAl₂O₄,CaAl₂O₄, CoAl₂O₄, hexagonal boron nitride, one or more boron nitridenanotubes, and/or one or more carbon nanotubes.

Active Metal Nanoparticles

One or more nanoparticles may be used to decompose the ammonia. The oneor more nanoparticles may comprise an active metal configured todecompose or facilitate the decomposition of the ammonia. In some cases,the active metal nanoparticles may comprise, for example, ruthenium(Ru). The nanoparticles may comprise one or more binding sites (alsoreferred to herein as active sites) for ammonia to attach to. Thebinding sites may be determined based on a shape, a morphology, and/or asurface chemistry or property of the active metal nanoparticles. Asdescribed herein, the morphology of the active metal nanoparticles maycorrespond to a size, shape, pore structure, pore size, pore shape, porevolume, pore density, pore size distribution, grain structure, grainsize, grain shape, crystal structure, flake size, or layered structureof the one or more active metal nanoparticles. As described herein, thephysical or chemical property of the active metal nanoparticles maycomprise an Arrhenius acidity or basicity, a Lewis acidity or basicity,an electron density, an electronic state, or a hydrophilicity orhydrophobicity of the one or more active metal nanoparticles. One ormore ammonia particles may attach to the binding sites of the activemetal nanoparticles. The active metal nanoparticles may be configured tobreak the nitrogen-hydrogen (N—H) bonds of ammonia. The morphologyand/or surface chemistry or property of the active metal nanoparticlesmay enhance ammonia adsorption, the breakdown (or scission) of N—Hbonds, and hydrogen and/or nitrogen desorption.

Morphology

The morphology of the nanoparticles may be improved. The morphology maycomprise a structure, a size, an aspect ratio, a facet distribution,and/or a shape of the nanoparticles. In some cases, the morphology maycomprise a grain structure, grain sizes, and/or grain boundaries. Insome cases, the morphology may correspond to a size, shape, porestructure, pore size, pore shape, pore volume, pore density, pore sizedistribution, grain structure, grain size, grain shape, crystalstructure, flake size, or layered structure of the one or more activemetal nanoparticles. The morphology of the nanoparticles may becustomized or changed to improve the locations and/or the availabilityof the active sites on a molecular level. The binding sites or theactive sites of the nanoparticles may be defined or determined in partbased on the morphology of the nanoparticles.

Surface Chemistry

The chemical and/or physical properties of the nanoparticles may beimproved. The chemical and/or physical properties may comprise, forexample, a surface chemistry or property of the one or more active metalnanoparticles. The physical and/or chemical property of the active metalnanoparticles may comprise, for example, an Arrhenius acidity orbasicity, a Lewis acidity or basicity, an electron density, anelectronic state, or a hydrophilicity or hydrophobicity of the one ormore active metal nanoparticles. The surface chemistry or property ofthe nanoparticles may be customized or changed to improve the locationsand/or the availability of the active sites on a molecular level. Thebinding sites or the active sites of the nanoparticles may be defined ordetermined in part based on the surface chemistry or properties of thenanoparticles.

Form Factor

In some embodiments, the catalyst support material may comprise a porousmaterial. In some instances, the catalyst support material may comprisea two-dimensional material. In some embodiments, the catalyst may beprovided as a coating on a bead or a pellet. This may solve the issue ofcompressing powdered catalysts into a bead or a pellet form but notbeing able to use all of the catalyst material in the body of the beador pellet. In some cases, the catalyst may be provided as a coating on apowder. In some cases, the catalyst may be provided as a coating on aporous monolith or a solid foam material. The coating may be improvedwith a predetermined amount of catalyst material to ensure that at leasta threshold amount of the catalyst material is used. The thresholdamount may be, for example, at least about 75, 80, 85, 90, 95, or 99% byweight or volume. A plurality of beads or pellets comprising a catalystmaterial coating may be used in combination with a reformer to decomposeor crack ammonia to generate hydrogen.

Process and Pore Modification

FIG. 4 schematically illustrates an example process for modifying andenhancing a catalyst support. A catalyst support may be provided. Thecatalyst support may comprise any one or more metals (e.g., aluminum),nonmetals, and/or metalloids. In some cases, the pores of the catalystsupport material may be modified. Modifying the pores may comprise, forexample, modifying a pore size, a pore density, a pore volume, or alocation or distribution of the pores through an area or a volume of thecatalyst support material. The pores may be modified chemically (e.g.,using corrosive gases or liquid chemicals to selectively etch out pores)or physically (e.g., using one or more thermal treatments under variousgases). In some cases, the thermal treatments may change a phase or astate of the catalyst support material, which may also change the poresize of the catalyst support material. In some cases, the pore sizes maybe modified differently for different types of reactions or fordifferent types of performance characteristics. In some cases, thethermal treatments may be accompanied by an exposure of the catalystsupport material to one or more reactive gases. In some cases, thereactive gases may comprise gases containing one or more of nitrogen(e.g. NO, NO₂, NH₃, HCN), sulfur (H₂S, SO₂), chlorine (Cl₂, HCl), carbon(CO, CO₂), fluorine, or gases generated from plasma such as ozone.

Fabrication of a Composite Support

In some embodiments, the surface of the catalyst support may be modifiedor coated. In some cases, the catalyst support material comprising themodified pore characteristics may be coated with an intermediate layerthat can act as a platform for one or more active metals or active metalparticles to grow. The intermediate layer can be used to change orinfluence a morphology of the active metal nanoparticles once the activemetal nanoparticles are provided on the intermediate layer. In somecases, the intermediate layer may comprise a composite support material.The composite support material may be deposited on the catalyst supportmaterial using vapor deposition (e.g., chemical vapor deposition orphysical vapor deposition). In some cases, the composite supportmaterial may be deposited on the catalyst support material bysputtering.

The composite support material may comprise a morphology and a physicalor chemical property (e.g., a surface chemistry). The morphology and/orthe physical or chemical properties of the composite support materiallayer may be used to change or influence the morphology and the physicalor chemical properties of the active metal nanoparticles deposited ontop of the composite support material. In some cases, the active metalnanoparticles may grow while conforming to the morphology and thephysical or chemical properties of the composite support material layer.

In some cases, the catalyst support material may comprise a morphologyand a physical or chemical property (e.g., a surface chemistry). Themorphology and/or the physical or chemical properties of the catalystsupport material layer may be used to change or influence the morphologyand the physical or chemical properties of the active metalnanoparticles deposited on top of the catalyst support material or thecomposite support material. In some cases, the active metalnanoparticles may grow while conforming to the morphology and thephysical or chemical properties of the catalyst support material and/orthe composite support material layer.

In some cases, the catalyst support may comprise one or more propertiesor characteristics that may be improved using one or more physical orchemical processes. The one or more properties or characteristics maycomprise, for example, a morphology or a surface chemistry or propertyof the catalyst support. The morphology may comprise a pore structure, apore size, a pore shape, a pore volume, a pore density, a pore sizedistribution, a grain structure, a grain size, a grain shape, a crystalstructure, a flake size, or a layered structure. The surface chemistryor property may comprise an Arrhenius acidity or basicity, a Lewisacidity or basicity, a surface hydroxyl group density, or ahydrophilicity or hydrophobicity. In some cases, the morphology or thesurface chemistry or property of the composite support material mayconform to a morphology or a surface chemistry or property of thecatalyst support. In some cases, the morphology or the surface chemistryor property of the active metal nanoparticles may conform to themorphology or the surface chemistry or property of the catalyst supportmaterial and/or the composite support material. In some cases, themorphology or the surface chemistry or property of the composite supportmaterial may conform to the morphology or the surface chemistry orproperty of the catalyst support material.

In some cases, CVD may be used to deposit a composite support materialcomprising boron nitride on the catalyst support. A thin layer of thecomposite support material may be deposited on a surface layer of thecatalyst support. CVD may be used to create a network of the compositesupport material on the existing catalyst support and/or within one ormore pores of the catalyst support material. In some cases, thecomposite support material may comprise various metal oxides (e.g.,titanium oxide or one or more other two-dimensional (2D) orthree-dimensional (3D) materials).

Depositing the composite support material as an additional layer on topof the catalyst support may be advantageous over the use of a powderform of the composite support material, since a powder form may bedifficult to use in a reformer due to the resulting pressure drop.Although compressing the powder into a pellet form can solve pressuredrop issues, the composite support materials within the body of thepellet may not be fully utilized, which is wasteful and inefficient. Insome cases, a powder may refer to a granular substance comprising asignificant portion of particles that comprise sizes less than 1 mm in acharacteristic dimension (length or diameter) or aspect ratio. In somecases, the aspect ratio may be at least about 1:5, 1:4, 1:3, 1:2, 1:1,2:1, 3:1, 4:1, 5:1, 10:1, 15:1, 20:1, 25:1, 30:1, 35:1, 40:1, or 45:1.In some cases, the aspect ratio may be not more than about 1:4, 1:3,1:2, 1:1, 2:1, 3:1, 4:1, 5:1, 10:1, 15:1, 20:1, 25:1, 30:1, 35:1, 40:1,45:1 or 50:1. In some cases, the significant portion may be at leastabout 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, 95, 99 by wt %, vol %, or %by count. In some embodiments, the significant portion may be not morethan about 10, 20, 30, 40, 50, 60, 70, 80, 90, 95, or 99 by wt %, vol %,or % by count.

Addition of Active Metal

After the composite support material is deposited on the catalystsupport material, the one or more active metals may be deposited on thecatalyst support material and/or the composite support material. Theactive metals may be deposited using CVD. The active metals may bedeposited on top of the composite support and also within the one ormore modified pores of the catalyst support material as active metalnanoparticles. This may facilitate decomposition of any ammoniamolecules that penetrate through the pores of the catalyst support. Thedeposition of the active metal nanoparticles on the composite supportmay also be referred to herein as an impregnation of the compositesupport with one or more active metal nanoparticles.

Once deposited on or within the catalyst support material and/or thecomposite support material, the active metal nanoparticles may growaccording to a morphology and/or a physical or chemical property of thecomposite support material. In some cases, the composite supportmaterial may comprise a hexagonal shaped grain. The active metalnanoparticles may grow while maintaining a grain shape corresponding tothe grain shape of the composite support material. In some cases, theactive metal nanoparticles may grow while maintaining a hexagonal grainshape. The composite support material may provide a 2D structure orplatform for ruthenium growth. The ruthenium may grow while conformingto a structure of the composite support material. In some instances, thecomposite support material may comprise boron nitride. The Ruthenium maygrow while maintaining the hexagonal morphology of the composite supportmaterial. In some cases, the catalyst may undergo one or more thermaltreatments in a vacuum state (i.e., below atmospheric pressure) and/orin the presence of various gases such as hydrogen gas or ambient air.Such thermal treatments may be used to thermally activate the activemetal nanoparticles embedded in the composite support structure tofacilitate the change in the morphology and/or the physical or chemicalproperties of the active metal nanoparticles to conform to themorphology and/or the physical or chemical properties of the materialsor particles (e.g., atoms or molecules) constituting the compositesupport.

Use of Promoters with Active Metals

In some cases, the composite material and/or the one or more activemetal nanoparticles embedded in the composite material may be promoted(e.g., with cesium) to change an electron state or an electron densityof the active metal nanoparticles. As described above, the active metalnanoparticles may comprise, for example, ruthenium. In some cases, themodified electron state or electron density may facilitate recombinativenitrogen desorption and/or N—H bond cleavage during an ammoniadecomposition reaction

The methods and processes disclosed herein for fabricating compositecatalysts may be implemented to produce catalysts with one or moredesirable properties or performance characteristics (e.g., efficienthydrogen production). The catalysts may lower the activation energybarrier for the ammonia decomposition reactions, and can facilitatereactions at lower temperatures while increasing throughput andenhancing the efficient utilization of precious metals. The presentlydisclosed methods and processes may be adapted and scaled for economicalmass fabrication of high performance, highly efficient catalysts.

FIG. 5 shows an example method for synthesizing the one or more activemetal nanoparticles. In some cases, the active metal nanoparticles maybe fabricated from a precursor material (e.g., a precursor materialcomprising ruthenium). The active metal nanoparticles may be promotedwith one or more alkali metals. The promoters may comprise one or moresubstances (e.g., co-catalysts) that can be added to increase ammoniaconversion efficiency or selectivity. The one or more active metalnanoparticles may undergo one or more thermal treatments that thermallyactivate the active metal nanoparticles so that the active metalnanoparticles undergo growth and a change in morphology orphysical/chemical property to mirror the morphology and/or the physicalor chemical properties of the composite support material in which or onwhich the active metal nanoparticles are deposited. The systems andmethods described herein may be used to control the morphology, surfacechemistry, and/or the dispersion of the active metal nanoparticles, andto control interactions between the active metal nanoparticles and thecomposite support or catalyst support. The systems and methods of thepresent disclosure may also be used to improve one or more active siteson the active metal nanoparticles for breaking down and decomposing orcracking one or more ammonia molecules.

The improved catalysts described herein may exhibit enhanced ammoniadecomposition performance and increased ammonia conversion efficiencies.The ammonia conversion efficiency for the improved catalysts may be afunction of reaction temperature. In some cases, the ammonia conversionefficiency may reach up to at least about 90% at reaction temperaturesof about 500° C. In some cases, the ammonia conversion efficiency mayrange from about 70% to about 99% at reaction temperature ranging fromabout 300° C. to about 600° C.

Thermal and Chemical Treatment of Supports

In some instances, the catalyst fabrication methods may comprise athermal treatment under reactive gases. Such thermal treatment may beused to modify the porosity of the support for improved mass transfer.Such thermal treatment may also be used to modify one or more propertiesof the support (e.g., the basicity or acidity of the support) for bettersurface modification results.

In some embodiments, the catalyst fabrication methods may comprise asurface modification and coating step. The surface modification andcoating step may comprise an intermediate layer deposition by PVD orCVD. PVD or CVD may be used to coat a support geometry with a thin,uniform layer of functional materials. The coating layer may have athickness that ranges from about at least about 1 nm to about 20 nm ormore. The functional materials may serve as a platform for nanoparticlegrowth. In some cases, the morphology and/or the physical or chemicalproperties of the functional materials may influence a growth and/or amorphology or a surface chemistry of the nanoparticles.

In some instances, the catalyst fabrication methods may compriseimpregnation of active metal nanoparticles. The impregnation maycomprise precursor impregnation with vacuum vapor deposition orincipient wet impregnation. This can allow for control of the precursoranchoring on the functional materials.

In some embodiments, the catalyst fabrication methods may comprisepromoting and thermal, physical, chemical or electrochemical activation.Promoting may comprise impregnation of promoter materials (e.g., alkalimetals and or alkaline-earth metals) into the active metal and/orcomposite support material to facilitate electron density modificationand modification or improvement of a morphology or an active site of thecatalyst. Thermal and/or chemical activation may also be used to modifythe morphology of the active metal nanoparticles under a reducingenvironment (e.g., an environment comprising hydrogen gas) or in thepresence of one or more noble gases.

FIG. 6A schematically illustrates the effects of reducing Ru-aluminacatalysts on ammonia conversion efficiency, in accordance with someinstances of the present disclosure. The catalysts of the presentdisclosure may be doped, promoted and/or thermally treated in anappropriate manner to improve catalyst performance and ammoniaconversion efficiency. Compared to a bare sample catalyst (i.e., acatalyst that has not undergone doping, promotion and/or thermaltreatment), a catalyst that has been doped, promoted and thermallytreated may exhibit a higher ammonia conversion efficiency. A highertemperature or treatment time may result in better performance of thecatalyst. For example, a bare sample catalyst may exhibit up to about a30% ammonia conversion efficiency at temperatures of about 500° C.Surprisingly, a catalyst that has been doped, promoted and thermallytreated at 700° C. may exhibit at least about a 60% ammonia conversionefficiency or more at temperatures of about 500° C. Unexpectedly, acatalyst that has been doped, promoted and thermally treated at 900° C.may exhibit at least about an 80% ammonia conversion efficiency or moreat temperatures of about 500° C.

Described herein is an example of the effect of reduction temperatureand duration on hydrogen generation or production rates, in accordancewith some embodiments. In some cases, catalyst performance may beimproved by a factor of about 2 or more, by higher temperature and/orlonger duration thermal treatment under H₂. With reference to FIG. 6B,shown here is a base Ru-alumina catalyst 601, with no dopant or thermaltreatment that may have a hydrogen generation rate that may be not morethan about 125 mmol_(H2) g_(cat) ⁻¹ h⁻¹ (mmol of hydrogen per gram ofcatalyst material per hour). The base catalyst can be treated with adopant (“X”) before the Ru is deposited 602, and this may have ahydrogen generation rate that is about 150 mmol_(H2) g_(cat) ⁻¹ h⁻¹.Treatment in a NH₃ atmosphere may improve the base catalyst may hydrogengeneration rate that is about 150 mmol_(H2) g_(cat) ⁻¹ h⁻¹ 604.Alternatively, the base catalyst may be thermally treated in a H₂atmosphere at 700° C. for 20 hours 606 or for 40 hours 608, or for 9hours at 900° C. 610, increasing the hydrogen generation rates up toabout 175, 200 and 250 mmol_(H2) g_(cat) ⁻¹ h⁻¹, respectively.

FIG. 6C schematically illustrates the effects of active metal promotionof catalysts on ammonia conversion efficiency, in accordance with someembodiments of the present disclosure. The catalysts of the presentdisclosure may be promoted with one or more alkaline metals. In somecases, cesium may be one of the most effective promoters for X-Al₂O₃catalysts. However, in some cases, excessive promotor incorporation maydeteriorate catalyst performance and hydrogen generation or productionrates. As such, an improved promoter amount exists for catalystmaterials. The catalysts of the present disclosure may be doped,promoted and/or thermally treated in an appropriate manner to improvecatalyst performance and hydrogen generation or production rates.

In some cases, a bare sample catalyst may exhibit an ammonia conversionefficiency of at most about 20% at temperatures of about 500° C. Acatalyst that has been promoted with potassium may exhibit an ammoniaconversion efficiency that is at least about 60% or more at temperaturesof about 500° C. A catalyst that has been promoted with cesium mayexhibit an ammonia conversion efficiency that is at least about 85% ormore at temperatures of about 500° C.

FIG. 6D schematically illustrates the effects of doping base Ru-ammoniacatalysts on ammonia conversion efficiency and hydrogen generation orproduction rate, in accordance with some embodiments. Surprisingly, acatalyst with more effective levels of promoter for the active metalcontent may exhibit an ammonia conversion efficiency that is at leastabout 85% or more at temperatures of about 500° C. On the other hand,catalysts with lower or higher promoter levels may have a reducedammonia conversion efficiency (e.g., from about 20% to about 60% orless).

Described herein is an example of the effect of promoter concentrationand molar ratio of active metal to the promoter, for some Ru-aluminacatalysts. Compared to the base Ru-alumina catalyst, inclusion ofpromoter at a 1:1 molar ratio of active metal and promoter improvedcatalyst performance, compared to the same catalyst without promoter. Aspromoter concentration increases to a more effective molar ratio ofactive metal to promoter (e.g., 1:3), catalyst performance continues toimprove. However, increasing the promoter concentration still further,catalyst performance unexpectedly reduces to below the base level.Surprisingly, additional thermal treatment may further improve catalystperformance when the more effective molar ratio of active metal andpromoter is used.

With reference to FIG. 6E shown here is the base Ru-alumina catalyst611, with no promoter or thermal treatment, that exhibits a hydrogengeneration rate of not more than about 175 mmol_(H2) g_(cat) ⁻¹ h⁻¹,612. The base catalyst may be doped with a promoter (Cs) to achieve amolar ratio of Ru and Cs of 1:1, increasing the hydrogen generation rateup to about 300 mmol_(H2) g_(cat) ⁻¹ h⁻¹, 612. The base catalyst may bedoped with a higher concentration of promoter, to achieve a molar ratioof Ru and Cs of 1:3, 613, and may be further subjected to additionalthermal treatment 615, resulting in hydrogen generation rates of up toabout 460 and 500 mmol_(H2) g_(cat) ⁻¹ h⁻¹, respectively. Increasing theconcentration of promoter still further, to a molar ratio of Ru and Csof 1:6, significantly reduces hydrogen rate to not more than about 100mmol_(H2) g_(cat) ⁻¹ h⁻¹, 614.

Materials

In any of the embodiments described herein, the catalyst supportmaterials may comprise, for example, a metal oxide-based support havingone or more micropores or mesopores. In some cases, the supportmaterials may comprise, for example, aluminum oxide (Al₂O₃) or nickel(Ni) based metal foams. In some instances, the catalyst support materialmay comprise one or more of aluminum oxide (Al₂O₃), magnesium oxide(MgO), cerium dioxide (CeO₂), silicon dioxide (SiO₂), silicon carbide(SiC), yttrium oxide (Y₂O₃), one or more zeolites (e.g., MFI zeolite,MCM-41 zeolite, Y type zeolite, X type zeolite), titanium dioxide(TiO₂), zirconium dioxide (ZrO₂), lanthanum oxide (La₂O₃), or chromiumoxide (Cr₂O₃). In some embodiments, the catalyst support material maycomprise one or more of Al_(x)O_(y), Mg_(x)O_(y), Ce_(x)O_(y),Si_(x)O_(y), Y_(x)O_(y), Ti_(x)O_(y), Zr_(x)O_(y), La_(x)O_(y), orCr_(x)O_(y).

In any of the embodiments described herein, the composite coatingmaterials may comprise a carbon-based material, a boron-based material,or a metal oxide. The carbon-based material may comprise, for example,activated carbon (AC), one or more carbon nanotubes (CNT), carbonnanofibers (CNF), graphene oxide (GO), graphite, one or more carbonnanoribbons, or reduced graphene oxide (rGO). The boron-based materialmay comprise, for example, hexagonal boron nitride (hBN), boron nitridenanotubes (BNNT), or boron nitride nanosheets (BNNS). The metal oxidemay comprise, for example, TiO₂, MgO, La₂O₃, CeO₂, Y₂O₃, one or moreCeO₂ nanotubes, nanorods or nanocubes, mesoporous silica (e.g., KIT-6),or ZrO₂.

In any of the embodiments described herein, the active metals or theactive metal nanoparticles may comprise, for example, ruthenium (Ru),nickel (Ni), cobalt (Co), iron (Fe), copper (Cu), molybdenum (Mo),iridium (Ir), rhenium (Re), platinum (Pt), or palladium (Pd). The one ormore active metals may be fabricated from one or more precursormaterials. The precursor materials may comprise, for example, RutheniumChloride (RuCl₃), Ruthenium Nitrosylnitrate (Ru(NO)(NO₃)₃), Trirutheniumdodecacarbonyl (Ru₃(CO)₁₂), Ruthenium acetylacetonate (Ru(acac)₃),Ruthenium nitrate (Ru(NO₃)₃), Ruthenium hexaammine chloride(Ru(NH₃)₆Cl₃), Cyclohexadiene ruthenium tricarbonyl ((CHD)Ru(CO)₃),Butadiene ruthenium tricarbonyl ((BD)Ru(CO)₃), or Dimethyl butadieneruthenium tricarbonyl ((DMBD)Ru(CO)₃).

As described above, in some cases one or more promoter(s) or promotingmaterials may be used to modify or enhance an electron density of theactive metal nanoparticles and/or the composite support material. In anyof the embodiments described herein, the one or more promoters orpromoting materials may comprise, for example, cesium (Cs), rubidium(Rb), potassium (K), sodium (Na), barium (Ba), strontium (Sr), calcium(Ca), or magnesium (Mg). In some cases, excessive concentrations ofpromoter materials may deteriorate the catalyst performance and ammoniaconversion efficiency (i.e., improved amount of doping material exists).As discussed above, the catalysts of the present disclosure may have oneor more promoters added therein in appropriate amounts or relativeconcentrations to improve catalyst performance and ammonia conversionefficiency.

In some instances, one or more layers of a composite material may becoated on the catalyst support material. The composite material maycomprise one or more layers of boron nitride. The one or more layers mayhave a thickness of at most about 10 nm.

In some embodiments, the catalyst support with the layer of compositematerial deposited on the catalyst support may be impregnated with oneor more active metal nanoparticles. In some cases, the active metalnanoparticles may be deposited on the composite layer, and themorphology of the active metal nanoparticles may be modified bysubjecting the nanoparticles to one or more thermal treatment methods.In some cases, the nanoparticles may have a size ranging from about 1 nmto about 50 nm. In some cases, the dispersion of the nanoparticles mayrange from about 10% to about 60%. As used herein, dispersion may referto the number of active metal atoms that are exposed on a surface of theactive metal nanoparticles relative to the total number of atomsconstituting the catalyst or a surface area or volume of the catalyst.The active metal atoms that are exposed on a surface of the catalyst maybe capable of binding with one or more ammonia molecules using one ormore active sites (also referred to herein as binding sites) of theactive metal nanoparticles. As described herein, the active sites orbinding sites of the active metal nanoparticles may be improved bysubjecting the active metal nanoparticles to one or more thermaltreatments that allow the active metal nanoparticles to adopt amorphology of the particles constituting the composite material layer.

In some cases, the improved catalysts disclosed herein may have ahydrogen production rate that is greater than that of conventionalruthenium catalysts. The hydrogen production rate based on the activemetal content of the improved catalysts may be greater than that ofconventional catalysts by a factor of at least about 1, 2, 3, 4, 5, 6,7, 8, 9, 10, or more. In some cases, the improved catalysts may exhibitat least about a 90% conversion efficiency of ammonia to hydrogen at450° C. and a space velocity of under 10 liters per hour per gram ofcatalyst. In some cases, the improved catalysts may exhibit at leastabout a 90% conversion efficiency of ammonia to hydrogen at 450° C. anda space velocity of at least about 1, 2, 4, 6, 8, 10, 12, 14, 15, 16,18, 20, 22, 24, 26, 28, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85,90, or 95 liters per hour per gram of catalyst. In some cases, theimproved catalysts may exhibit at least about a 90% conversionefficiency of ammonia to hydrogen at 450° C. and a space velocity of atmost about 2, 4, 6, 8, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65,70, 75, 80, 85, 90, 95, or 100 liters per hour per gram of catalyst. Insome cases, the improved catalysts may produce hydrogen and nitrogenwith an ammonia conversion efficiency of from about 70 to about 99.9, 70to 99, 70 to 98, 70 to 97, 70 to 96, 70 to 95, 70 to 90, 75 to 99.9, 75to 99, 75 to 98, 75 to 97, 75 to 96, 75 to 95, 75 to 90, 80 to 99.9, 80to 99, 80 to 98, 80 to 97, 80 to 96, 80 to 95, 80 to 90, 85 to 99.9, 85to 99, 85 to 98, 85 to 97, 85 to 96, 85 to 95, 85 to 90, 90 to 99.9, 90to 99, 90 to 98, 90 to 97, 90 to 96, 90 to 95, 95 to 99.9, 95 to 99, 95to 98, 95 to 97, or 95 to 96%, at a temperature of at least about 450°C. and not more than about 700° C., and a space velocity of from about 1to about 100 L_(gas) hr⁻¹ g_(cat) ⁻¹. In some cases, the improvedcatalysts may exhibit a nitrogen desorption activation energy that isless than that of conventional ruthenium catalysts.

Reformers and Power Systems Using Improved Catalysts

The catalysts of the present disclosure may be used compatibly withvarious power systems (e.g., reformers) for decomposing or crackingammonia to generate hydrogen. The power systems may comprise, forexample, one or more reformers that can perform a catalyticdecomposition or cracking of ammonia to extract and/or produce hydrogen.Such reformer may be operated using heat energy. In some cases, thepower system may comprise a combustor that generates heat energy todrive the operation of the reformer. In some cases, the heat energy maybe generated from the combustion of a chemical compound (e.g., hydrogenor a hydrocarbon).

In some cases, the reformer may comprise an outlet configured to directone or more fluids (e.g., ammonia, nitrogen, and/or hydrogen) to anothersystem or subsystem. In some cases, the outlet may be configured todirect hydrogen gas produced by the reformer to one or more fuel cellsand/or to one or more combustion engines. In some cases, the outlet maybe configured to direct hydrogen gas produced by the reformer to one ormore combustors to generate heat energy that can be used to power orheat the reformer (e.g., for autothermal heating or self-heating). Insome cases, the outlet may be configured to direct hydrogen, nitrogen,and/or ammonia to at least one other reformer (e.g., for combustion ofthe hydrogen to heat the at least one other reformer).

Use of Produced Hydrogen in Fuel Cells or Engines

The hydrogen generated using the improved catalysts of the presentdisclosure may be provided to one or more fuel cells or proton-exchangemembrane fuel cells (PEMFC) to generate electrical energy. The hydrogengenerated using the improved catalysts of the present disclosure mayalso be provided to one or more combustion engines to generatemechanical work or mechanical energy. The hydrogen that is generatedand/or extracted using the reformer may be provided to one or more fuelcells or to one or more combustion engines, which may produce electricalenergy or mechanical work to power one or more systems, sub-systems, ordevices requiring electrical or mechanical energy to operate. In somecases, partially generated and/or extracted hydrogen and nitrogen from areformer and at least a portion of the remaining ammonia mixture may beprovided to one or more other reformers to enable a continuous reformingprocess. The partially generated and/or extracted hydrogen and nitrogenand the remaining ammonia may be part of a partially cracked stream ofammonia. The partially cracked stream of ammonia may be generated usinga reformer having less than a 100% ammonia conversion efficiency. Thepartially cracked stream may be passed to one or more downstreamreformers to minimize material waste and maximize an amount of ammoniathat can be decomposed or cracked. In some cases, the hydrogen generatedand/or extracted using the reformer may be provided to one or more otherreformers. In such cases, the one or more other reformers may beconfigured to combust the hydrogen to generate additional thermalenergy. Such additional thermal energy may be used to heat the one ormore other reformers to facilitate a further catalytic decomposition orcracking of ammonia to extract and/or produce additional hydrogen.

Resistance Heating of Catalyst in Reformer

In some cases, the reformers may be configured to heat up the improvedcatalysts directly using resistance heating (e.g., by passing a currentthrough the catalyst itself or through the catalyst support). In suchcases, the reformers may comprise one or more electrodes for passing acurrent through the catalyst to heat the catalyst (e.g., by resistiveheating or Joule heating). The one or more electrodes may comprise, forexample, one or more metal (e.g., copper, steel, titanium, or carbon)electrodes. In other cases, the reformers may be configured to heat upthe improved catalysts by combusting hydrogen. The improved catalystsmay be configured to decompose ammonia into hydrogen and/or nitrogenwhen heated by combustion or resistance heating.

In some cases, the reformers may comprise one or more electricallyconductive springs. The one or more electrically conductive springs maybe provided adjacent to the improved catalysts disclosed herein. In somecases, the one or more electrically conductive springs may be providedon opposite ends of the catalyst. The one or more electricallyconductive springs may be in physical, electrical, and/or thermalcommunication with the catalyst, the catalyst bed, and/or the one ormore electrodes used to perform direct resistive heating of thecatalyst. The one or more electrically conductive springs may beconfigured to reduce thermal stresses on the catalyst when the catalystis subjected to thermal cycling. The one or more electrically conductivesprings may be configured to accommodate thermal expansions duringheating of the catalyst and thermal contractions during cooling of thecatalyst. The one or more electrically conductive springs may lightenand/or redistribute the mechanical load on the catalyst bed so that thecatalyst bed can withstand multiple thermal cycles without breaking orfracturing. In some cases, the one or more springs may be configured toalleviate thermal stresses on the catalyst due to a thermal expansion ora thermal contraction of the catalyst during one or more thermal cyclingprocedures. The one or more springs may comprise, for example, stainlesssteel, titanium, or copper springs. The use of the one or moreelectrically conductive springs may allow the reformer to provide faststartup capabilities with reduced or minimal thermal stresses on thecatalyst bed during rapid temperature changes.

Hybrid Heating System

In some cases, the improved catalysts may undergo hybrid heating withina reformer. Such hybrid heating can improve heat transfer whileminimizing reformer heat loss and increasing startup time. A hybridheating design can also reduce a weight and a volume of the reformer andimprove thermal management characteristics of the system while providingan improved heat source for ammonia conversion.

In some cases, the improved catalysts may be heated using one or moreheat sources. In some cases, the one or more heat sources may comprisetwo or more heat sources or heating units. In some cases, the two ormore heat sources may be the same or similar. In other cases, the two ormore heat sources may be different. For example, a first heat source maybe configured for joule heating, and a second heat source may beconfigured for combustion.

In some cases, the improved catalysts may be heated using a plurality ofheating units. The plurality of heating units may comprise a firstheating unit configured to heat at least a first portion of a catalystby combusting hydrogen and a second heating unit configured to heat atleast a second portion of the catalyst using electrical heating. Theterm “electrical heating,” as used herein, generally refers to heatingperformed at least in part by flowing electrons through a material(e.g., an electrical conduit). The electrical conduit may be a resistiveload. In some examples, electrical heating may comprise Joule heating(i.e., heating that follows Ohm's law). Joule heating, also known asresistive, resistance, or Ohmic heating, may comprise passing anelectric current through a material (e.g., the electrical resistor, thecatalyst, the catalyst material, or the catalyst bed) to produce heat orthermal energy. In some cases, the catalyst may be used to generatehydrogen from a source material comprising the ammonia when the catalystis heated using the plurality of heating units. In some instances, thefirst portion and the second portion may be the same portion of thecatalyst. In other instances, the first portion and the second portionmay be different portions of the catalyst. In some cases, the firstportion and the second portion may overlap or partially overlap.

In some cases, a first heating unit of a reformer may be configured toheat a first portion of the catalyst based on a combustion of hydrogengas generated using a secondary reformer. In some cases, the firstheating unit may be configured to heat the first portion of the catalystbased on a combustion of leftover hydrogen gas from (i) one or more fuelcells in fluid communication with the reformer or (ii) a secondaryreformer. In some cases, the second heating unit may be configured toheat a second portion of the catalyst by passing an electrical currentthrough the second portion of the catalyst. In some cases, the firstportion of the catalyst and the second portion of the catalyst may becontiguous (i.e., physical connected). In other cases, the first portionof the catalyst and the second portion of the catalyst may be separatedby a third portion of the catalyst. The third portion of the catalystmay be positioned between the first and second portions of the catalyst.In some cases, the first and second portions of the catalyst may be inthermal communication with each other (e.g., either directly orindirectly via the third portion of the catalyst). In other cases, thefirst and second portions of the catalyst may not or need not be inthermal communication with each other.

In some cases, a heat load distribution between the first heating unitand the second heating unit may be adjustable to increase an ammoniaconversion efficiency and/or to enhance a thermal efficiency of thereformer. The heat load distribution may comprise a heating power ratiocorresponding to a ratio between a heating power of the first heatingunit and a heating power of the second heating unit. The heating powerof the first heating unit and the second heating unit may be adjusted toachieve a desired ammonia conversion efficiency and thermal efficiency.In some cases, the system may further comprise a controller or processorconfigured to control an operation of the first heating unit and thesecond heating unit to adjust the heat load distribution within thereformer module. In some cases, such adjustments in the heat loaddistribution may be implemented in real-time based on one or more sensormeasurements (e.g., temperature measurements) or based on a performanceof the reformer (e.g., ammonia conversion efficiency and/or thermalefficiency of the reformer). In some cases, heaters with two or moreheating zones may be used to control power and heat distribution withinthe heater. In some cases, the system may comprise a plurality ofheating units.

The plurality of heating units may comprise at least two or more heatingunits. In some cases, a heat load distribution between the at least twoor more heating units may be adjustable to increase an ammoniaconversion efficiency and to enhance a thermal reforming efficiency ofthe reformer. In some cases, each of the at least two or more heatingunits may have one or more heating zones in the reformer to allow for acontinuous heat distribution within one or more regions in the reformermodule. In some cases, the at least two or more heating units may beconfigured to heat different zones in the reformer. In some cases, theat least two or more heating units may be configured to heat one or moresame zones in the reformer.

Computer Systems

The present disclosure provides computer systems (e.g., controllers,computing devices and/or computers) that are programmed to implementmethods of the disclosure. FIG. 7 shows a computer system 701 that isprogrammed or otherwise configured to control the systems disclosedherein. The computer system 701 can regulate various aspects of thesystems disclosed in the present disclosure. The computer system 701 canbe an electronic device of a user or a computer system that is remotelylocated with respect to the electronic device. The electronic device canbe a mobile electronic device.

The computer system 701 includes a central processing unit (CPU, also“processor” and “computer processor” herein) 702, which can be a singlecore or multi core processor, or a plurality of processors for parallelprocessing. The computer system 701 also includes memory or memorylocation 703 (e.g., random-access memory, read-only memory, flashmemory), electronic storage unit 704 (e.g., hard disk), communicationinterface 705 (e.g., network adapter) for communicating with one or moreother systems, and peripheral devices 706, such as cache, other memory,data storage and/or electronic display adapters. The memory 703, storageunit 704, interface 705 and peripheral devices 706 are in communicationwith the CPU 702 through a communication bus (solid lines), such as amotherboard. The storage unit 704 can be a data storage unit (or datarepository) for storing data. The computer system 701 can be operativelycoupled to a computer network (“network”) 707 with the aid of thecommunication interface 705. The network 707 can be the Internet, aninternet and/or extranet, or an intranet and/or extranet that is incommunication with the Internet. The network 707 in some cases is atelecommunication and/or data network. The network 707 can include oneor more computer servers, which can enable distributed computing, suchas cloud computing. The network 707, in some cases with the aid of thecomputer system 701, can implement a peer-to-peer network, which mayenable devices coupled to the computer system 701 to behave as a clientor a server.

The CPU 702 can execute a sequence of machine-readable instructions,which can be embodied in a program or software. The instructions may bestored in a memory location, such as the memory 703. The instructionscan be directed to the CPU 702, which can subsequently program orotherwise configure the CPU 702 to implement methods of the presentdisclosure. Examples of operations performed by the CPU 702 can includefetch, decode, execute, and writeback.

The CPU 702 can be part of a circuit, such as an integrated circuit. Oneor more other components of the system 701 can be included in thecircuit. In some cases, the circuit is an application specificintegrated circuit (ASIC).

The storage unit 704 can store files, such as drivers, libraries andsaved programs. The storage unit 704 can store user data, e.g., userpreferences and user programs. The computer system 701 in some cases caninclude one or more additional data storage units that are external tothe computer system 701, such as located on a remote server that is incommunication with the computer system 701 through an intranet or theInternet.

The computer system 701 can communicate with one or more remote computersystems through the network 707. For instance, the computer system 701can communicate with a remote computer system of a user. Examples ofremote computer systems include personal computers (e.g., portable PC),slate or tablet PC's (e.g., Apple® iPad, Samsung® Galaxy Tab),telephones, Smart phones (e.g., Apple® iPhone, Android-enabled device,Blackberry®), or personal digital assistants. The user can access thecomputer system 701 via the network 707.

Methods as described herein can be implemented by way of machine (e.g.,computer processor) executable code stored on an electronic storagelocation of the computer system 701, such as, for example, on the memory703 or electronic storage unit 704. The machine executable or machinereadable code can be provided in the form of software. During use, thecode can be executed by the processor 702. In some cases, the code canbe retrieved from the storage unit 704 and stored on the memory 703 forready access by the processor 702. In some situations, the electronicstorage unit 704 can be precluded, and machine-executable instructionsare stored on memory 703.

The code can be pre-compiled and configured for use with a machinehaving a processer adapted to execute the code, or can be compiledduring runtime. The code can be supplied in a programming language thatcan be selected to enable the code to execute in a pre-compiled oras-compiled fashion.

Aspects of the systems and methods provided herein, such as the computersystem 701, can be embodied in programming. Various aspects of thetechnology may be thought of as “products” or “articles of manufacture”typically in the form of machine (or processor) executable code and/orassociated data that is carried on or embodied in a type of machinereadable medium. Machine-executable code can be stored on an electronicstorage unit, such as memory (e.g., read-only memory, random-accessmemory, flash memory) or a hard disk. “Storage” type media can includeany or all of the tangible memory of the computers, processors or thelike, or associated modules thereof, such as various semiconductormemories, tape drives, disk drives and the like, which may providenon-transitory storage at any time for the software programming. All orportions of the software may at times be communicated through theInternet or various other telecommunication networks. Suchcommunications, for example, may enable loading of the software from onecomputer or processor into another, for example, from a managementserver or host computer into the computer platform of an applicationserver. Thus, another type of media that may bear the software elementsincludes optical, electrical and electromagnetic waves, such as usedacross physical interfaces between local devices, through wired andoptical landline networks and over various air-links. The physicalelements that carry such waves, such as wired or wireless links, opticallinks or the like, also may be considered as media bearing the software.As used herein, unless restricted to non-transitory, tangible “storage”media, terms such as computer or machine “readable medium” refer to anymedium that participates in providing instructions to a processor forexecution.

Hence, a machine readable medium, such as computer-executable code, maytake many forms, including but not limited to, a tangible storagemedium, a carrier wave medium or physical transmission medium.Non-volatile storage media include, for example, optical or magneticdisks, such as any of the storage devices in any computer(s) or thelike, such as may be used to implement the databases, etc. shown in thedrawings. Volatile storage media include dynamic memory, such as mainmemory of such a computer platform. Tangible transmission media includecoaxial cables; copper wire and fiber optics, including the wires thatcomprise a bus within a computer system. Carrier-wave transmission mediamay take the form of electric or electromagnetic signals, or acoustic orlight waves such as those generated during radio frequency (RF) andinfrared (IR) data communications. Common forms of computer-readablemedia therefore include for example: a floppy disk, a flexible disk,hard disk, magnetic tape, any other magnetic medium, a CD-ROM, DVD orDVD-ROM, any other optical medium, punch cards paper tape, any otherphysical storage medium with patterns of holes, a RAM, a ROM, a PROM andEPROM, a FLASH-EPROM, any other memory chip or cartridge, a carrier wavetransporting data or instructions, cables or links transporting such acarrier wave, or any other medium from which a computer may readprogramming code and/or data. Many of these forms of computer readablemedia may be involved in carrying one or more sequences of one or moreinstructions to a processor for execution.

The computer system 701 can include or be in communication with anelectronic display 708 that comprises a user interface (UI) 709 forproviding. Examples of UI's include, without limitation, a graphicaluser interface (GUI) and web-based user interface.

Methods and systems of the present disclosure can be implemented by wayof one or more algorithms. An algorithm can be implemented by way ofsoftware upon execution by the central processing unit 702.

Catalyst Fabrication Methods

In another aspect, the present disclosure provides a method forfabricating one or more catalysts for processing ammonia to generatehydrogen. The method may comprise subjecting a catalyst support to oneor more physical or chemical processes to modify one or more pores ofthe catalyst support. In some cases, the one or more physical orchemical processes for modifying the one or more pores of the catalystsupport may comprise a thermal treatment (i.e., controlled heating) ofthe catalyst support. In some cases, modifying the one or more pores maycomprise adjusting a size of the one or more pores, a pore density,and/or a pore volume of the catalyst support. In some cases, the methodmay further comprise thermally or chemically treating a surface of thecatalyst support material to modify the one or more pores and/or one ormore surface morphologies. In some cases, the catalyst support comprisesa bead, a pellet, a powder, a thin film, a monolith, a foam, reformerwall, heating element, wires, mesh, engineered or corrugated sheet, or aporous solid material form factor. In some cases, the catalyst ispowderless, for example, majority of the catalyst may be greater than 1mm in a characteristic dimension or aspect.

In some instances, the method may further comprise depositing acomposite support material on the catalyst support, wherein thecomposite support material comprises a morphology, and (c) depositingone or more active metals on at least one of the composite supportmaterial and the catalyst support, wherein the one or more active metalscomprise one or more nanoparticles configured to conform to themorphology of the composite support material, thereby improving one ormore active sites on the nanoparticles for ammonia processing. In somecases, the composite support material may be deposited using chemicalvapor deposition. In some cases, the one or more active metals may bedeposited using chemical vapor deposition. The active metals maycomprise one or more nanoparticles with one or more active sites towhich one or more ammonia molecules are attachable. The one or moreammonia molecules may be configured to bind or attach to the one or moreactive sites of the one or more active metal nanoparticles. Thepositions, orientations, and/or density of the one or more active sitesmay be determined based at least in part on a morphology and/or surfacechemistry or property of the composite support material. In someembodiments, the morphology may comprise a grain structure, a grainsize, or a grain shape.

In some cases, the catalyst support may comprise, for example, at leastone of Al₂O₃, MgO, CeO₂, SiO₂, SiC, Y₂O₃, TiO₂, or ZrO₂. In some cases,the catalyst support may comprise, for example, at least one ofAl_(x)O_(y), Mg_(x)O_(y), Ce_(x)O_(y), Si_(x)O_(y), Y_(x)O_(y),Ti_(x)O_(y), or Zr_(x)O_(y). In some cases, the one or more activemetals comprise, for example, at least one of ruthenium (Ru), nickel(Ni), rhodium (Rh), iridium (Ir), cobalt (Co), molybdenum (Mo), iron(Fe), platinum (Pt), chromium (Cr), palladium (Pd), or copper (Cu). Insome cases, the composite support may comprise a carbon-based material,a boron-based material, or a metal oxide. The carbon-based material maycomprise, for example, activated carbon (AC), one or more carbonnanotubes (CNT), one or more carbon nanofibers (CNF), graphene oxide(GO), graphite, or reduced graphene oxide (rGO). The boron-basedmaterial may comprise, for example, hexagonal boron nitride (hBN), boronnitride nanotubes (BNNT), or boron nitride nanosheets (BNNS). The metaloxide may comprise, for example, TiO₂, MgO, La₂O₃, CeO₂, Y₂O₃, one ormore CeO₂ nanotubes, nanorods or nanocubes, mesoporous silica (e.g.,KIT-6), ZrO₂, chromium oxide (Cr₂O₃), or calcium oxide (CaO). The metaloxide may comprise, for example, Ti_(x)O_(y), Mg_(x)O_(y), La_(x)O_(y),Ce_(x)O_(y), Y_(x)O_(y), Ce_(x)O_(y), Zr_(x)O_(y), Cr_(x)O_(y), orCa_(x)O_(y). In some cases, the composite support may comprise YSZ,Hydrotalcite (Mg₂Al-LDO), MOF (MIL-101, ZIFs), Alkaline amide (NaNH₂,Ca(NH₂)₂, Mg(NH₂)₂), Inorganic electride (C12A7:e-), Halloysitenanotubes (HNT), ABO3 Perovskite, AB2O4 Spinel, MCM-41.

In some cases, the method may further comprise thermally activating theone or more active metals. Thermally activating the one or more activemetals may induce a growth of one or more nanoparticles of the activemetals. In some cases, the one or more nanoparticles may be configuredto grow while conforming to the morphology of the composite supportmaterial. In some cases, the method may further comprise promoting thecatalyst, the active metal nanoparticles, and/or the composite supportmaterial of the catalyst with one or more promoters. The one or morepromoters may comprise, for example, sodium (Na), potassium (K),rubidium (Rb), cesium (Cs), magnesium (Mg), calcium (Ca), strontium(Sr), or barium (Ba).

Selection of Catalyst Precursors

In some cases, the ammonia decomposition reaction may be driven using acatalyst. The catalyst may comprise, for example, a rutheniumnanoparticle catalyst. The ruthenium nanoparticle catalyst may compriseone or more ruthenium nanoparticles. The ruthenium nanoparticle catalystmay be utilized to facilitate an ammonia decomposition reaction asdescribed herein, and may be fabricated by loading a given precursoronto an alumina carrier, or a modified alumina carrier, and performing areduction at a high temperature.

Support Precursors

In some cases, the support comprises an amorphous, monoclinic,tetragonal, hexagonal, or perovskite phase. In some cases, the modifiedsupport comprises an amorphous, monoclinic, tetragonal, hexagonal, orperovskite phase. In some cases, a metal salt or a metal salt hydrate,such as MNO₃, may be initially deposited on a surface of the aluminacarrier, followed by high-temperature calcination to generate an M-Aloxide support. As used herein, M may refer to any type of metal. In somecases, the M-Al oxide may form a perovskite phase, MAlO₃/Al₂O₃. In somecases, two or more types of metal salts or metal salt hydrates may beadded to generate a mixed M₁-M₂-Al oxide support. Onto this support, aruthenium precursor may be deposited, and the support and/or theruthenium precursor may be reduced at an elevated temperature (e.g., anelevated temperature ranging from about 500° C. to about 1200° C.) togenerate an improved nanoparticle catalyst. In some cases, a promotermay be added to the catalyst in the form of electron donors, e.g., Cs orK, which can further improve ammonia conversion efficiency.

Effect of Catalyst Support Form Factor

In some cases, the catalysts of the present disclosure may besynthesized using various alumina carriers. The alumina carriers may bein the form of a bead or a cylindrical pellet or a combination of both.In some cases, the alumina carrier may comprise any type of a poroussolid material. In other cases, the alumina carrier may comprise a bead,a pellet, a powder, a monolith, a foam, or any combination thereof.

Described herein is an example of the effect of support form factor onthe hydrogen generation performance of a Ru-alumina catalyst. Across atemperature range from about 400° C. to about 500° C., the catalystbased on 1.0 mm beads exhibited superior performance. Above atemperature of about 500° C., the difference between the catalyst using1.0 mm beads and the catalyst using 1.5 mm beads seems to reduce insignificance. The catalyst based on 3.2 mm pellets exhibits lowerperformance than the other two catalysts, across a temperature rangefrom about 400° C. to about 575° C. With reference to FIG. 8 ,Ru-alumina catalysts may be prepared according to the same methods andmaterials (described herein), and with the same composition. Thecatalysts may be prepared using RuCl₃ as the active metal precursor andon support material comprising gamma-alumina (γ-alumina). The catalystsmay comprise a form factor of: 1.0 mm beads 801, 1.5 mm beads 802, or3.2 mm pellets 803.

In some cases, a smaller particle size may lead to a more activecatalyst. In some cases, the bead or the pellet may have a diameterranging from about 0.1 mm to about 10 mm. In some cases, the bead or thepellet may have a surface area per unit mass ranging from about 50 m²/gto about 500 m²/g. In some cases, the bead or the pellet may have adiameter of at least about 0.1, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5,5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, or 9.5 mm. In some cases, the bead orthe pellet may have a diameter of at most about 0.5, 1, 1.5, 2.0, 2.5,3, 3.5, 4, 4.5, 5 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5 or 10 mm. In somecases, the bead or the pellet may have a surface area per unit mass ofat least about 50, 100, 150, 200, 250, 300, 350, 400, 450, 500, 550,600, 650, 700, 750, 800, 850, 900, 950, 1000, 1050, 1100, or 1150 m²/g.In some cases, the bead or the pellet may have a surface area per unitmass of at most about 100, 150, 200, 250, 300, 350, 400, 450, 500, 550,600, 650, 700, 750, 800, 850, 900, 950, 1000, 1050, 1100, 1150, or 1200m²/g.

Application of Dopants

There are many well-established techniques for the application of metaloxides and their precursors onto the surface of a support, to form amodified or doped support. Such techniques include: wet impregnation,template ion exchange, precipitation, sol-gel, citric acid process,deposition-precipitation, hydrothermal synthesis, chemical vapordeposition (CVD), physical vapor deposition (PVD), single atomcatalysts, thermal shock-high entropy alloy, galvanic exchange,ferromagnetic inductive heating and nanoparticle transfer.

Wet Impregnation Procedure

Wet (or wetness) impregnation may be a convenient technique, especiallyfor laboratory preparations, and the procedure is described here as anexample. Other techniques may also be used to prepare the catalysts ofthe present disclosure and should be considered as included by thisdisclosure.

Dopants may be applied to the support surface using separate solutions,with a drying step(s) between each application, or as a mixed solutionof dopant metal precursor(s). Mixed dopant and precursor solutions areunderstood to produce improved support characteristics for the finishedcatalyst. When applying solutions of mixed dopant precursors it isimportant to ensure compatibility between them to avoid unintentionalprecipitation. Alternatively, precipitation may be induced within thepore structure via sequential deposition of a dopant precursor followedby a precipitant. The promoter/precipitant precursor may also beincluded at this stage (e.g. KOH, or CsNO₃).

To dope the support material, an aqueous solution of the chosen metalprecursor(s) (e.g. La(NO₃)₃, Ce(NO₃)₄, and their hydrates) may beprepared, using e.g., deionized, distilled, or tap water. The mass ofeach dopant precursor(s) may be chosen to provide the desired metalloading on the support surface, and the volume of solvent water may bechosen to be about equal in mass to the support material, prior todeposition.

The steps involved in this procedure may include: (i) weigh the supportmaterial to determine its mass; (ii) knowing the chemical composition ofthe support, calculate the number of moles of support molecules (e.g.Al₂O₃, SiO₂, or ZrO₂) or key element (e.g. Al, Si, Zr, or C); (iii)calculate the number of moles of dopant metal required to achieve thedesired loading (mol %) or molar ratio on the support; (iv) prepare asolution of the dopant precursor(s) in the appropriate mass of water(about equal to the mass of the support material for incipient wetness).The number of moles of precursor (or metal ion) in the required volumeof water (calculated from the required mass) establishes the molarity ofthe solution with respect to the precursor (or metal ion). If excessprecursor solution is required, then the mass of water and precursor areincreased in proportion to the desired quantity.

Typically, the metal loading on the support may be expressed as mol % ofthe dopant metal. The metal loading on the support may be expressed as amolar ratio of the dopant metal(s) (e.g. La, or Ce) to each other or tothe support material (e.g. alumina or zirconia), and may range fromabout 1:10 to about 10:1. The desired loading of each dopant metal(s) onthe support may require a dopant solution concentration of from about0.01 Molar (M) to about 10M with respect to each dopant metal. The pH ofthe precursor solution may also be adjusted (with a suitable strong acidor base) to improve the effectiveness of the doping process, or theprecursor may be dissolved in a suitable, preprepared solution of anacid or base (e.g. 0.01M to 20M nitric acid, hydrochloric acid, aceticacid, sodium hydroxide, potassium hydroxide). The pH of the dopantsolution may be at least about pH 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11,12, 13, or 14. The pH of the dopant solution may be not more than aboutpH 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15.

The support material is immersed in the precursor solution for aduration of up to about 48 hours at ambient laboratory temperature(e.g., from about 15 to about 30° C.). If the pH of the dopant solutionhas been adjusted to a suitable range (e.g., about pH 1 to pH 2), therequired immersion time may be reduced to within the range of about 1 to2 hours. In some cases, the support material is immersed in theprecursor solution for a duration of up to about 48 hours at temperatureof at least about 0, 10, 20, 30, 40, 50, 60, 70, 80, 90, or 100° C. Insome cases, the support material is immersed in the precursor solutionfor a duration of up to about 48 hours at temperature of at most about0, 10, 20, 30, 40, 50, 60, 70, 80, 90, or 100° C. In some cases, thesupport material is immersed in the precursor solution at a temperatureof about 0° C. to about 100° C., for a duration of at least about 1, 2,3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, or 45 hours. In somecases, the support material is immersed in the precursor solution at atemperature of about 0° C. to about 100° C., for a duration of not morethan about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45, or48 hours.

The volume of the solution is selected to be at least equal to the totalpore volume of the support material (when these values are about equal,it is termed “incipient wetness”). A greater volume of solution may beunnecessary and may reduce the efficiency of the doping process, but maybe typically chosen when doping structured or monolith catalystsupports. At conclusion of the immersion time, the doped (wet) supportmaterial may be transferred to suitable equipment to remove or evaporatethe bulk solvent. A rotary evaporator (or rotovap) is a convenient andefficient apparatus to facilitate the removal of solvent at moderatetemperatures (e.g from about 20° C. to about 80° C.) below atmosphericpressure or in vacuo. The doped (wet) support may also be dried in alaboratory oven under vacuum or above atmospheric pressure, in whichcase higher temperatures (e.g. from about 80° C. to about 150° C.)and/or longer drying times may be required. Drying the doped support ina laboratory oven may also be performed as a supplemental step, beforeor after drying in other equipment (such as a rotary evaporator). Eachdrying step may be performed for up to 168 hours, depending on theconditions used.

Doping Conditions (Wet Impregnation)

In some embodiments, the dopant metal precursor(s) is applied to thesupport surface as one solution comprising, e.g. La(NO₃)₃, CeCl₃,Ce(HCO₃)₃, or Ce(CH₃COO)₃. In some embodiments, dopant metalprecursor(s) are applied to the support surface as separate solutions(with a drying step between each application). In some embodiments, theconcentration of the dopant metal precursor solution may comprise atleast about 0.01, 0.05, 0.1, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3,1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8,2.9, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, or 9.5M, withrespect to each dopant metal. In some embodiments, the concentration ofthe dopant metal precursor solution may comprise not more than about0.05, 0.1, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6,1.7, 1.8, 1.9, 2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3, 3.5,4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, or not more than 10M,with respect to each dopant metal.

Drying Conditions for Doped Support

In some embodiments, the doped support may be maintained at atemperature of at least about 10, 15, 20, 25, 30, 35, 40, 45, 50, 55,60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, 115, 120, 125, 130, 135,140, or 145° C., at a pressure of about 0.0001 to about 5 bar absolute,for a duration of about 0.1 to about 168 hours. In some embodiments, thedoped support may be maintained at a temperature of not more than about15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100,105, 110, 115, 120, 125, 130, 135, 140, 145, or 150° C., at a pressureof about 0.0001 to about 5 bar absolute, for a duration of about 0.1 toabout 168 hours.

In some embodiments, the doped support may be maintained at a pressureof at least about 0.0001, 0.001, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8,0.9, 1, 2, 3, or 4 bar absolute pressure, at a temperature of about 10°C. to about 150° C., for a duration of about 0.1 hours to about 168hours. In some embodiments, the doped support may be maintained at apressure of not more than about 0.001, 0.01, 0.1, 0.2, 0.3, 0.4, 0.5,0.6, 0.7, 0.8, 0.9, 1, 2, 3, or 4, or 5 bar absolute pressure, at atemperature of about 10° C. to about 150° C., for a duration of about0.1 hours to about 168 hours.

In some embodiments, the doped support may be maintained at atemperature of about 10° C. to about 150° C., and a pressure of about0.0001 bar absolute to about 5 bar absolute, for a duration of at leastabout 0.1, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 18, 24, 30, 36,42, 48, 60, 72, 84, 96, 108, 120, 132, 144, or 156 hours. In someembodiments, the doped support may be maintained at a temperature ofabout 10° C. to about 150° C., and a pressure of about 0.0001 barabsolute to about 5 bar absolute, for a duration of not more than about0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 18, 24, 30, 36, 42, 48, 60,72, 84, 96, 108, 120, 132, 144, 156 or 168 hours.

If separate dopant solutions are to be used, or if the promoterprecursor solution was not added during the wet impregnation process,then the immersion step and the drying step may need to be repeated foreach dopant and/or promoter precursor solution. Once the supportmaterial has been impregnated with all of the desired dopant metals,then the doped support may be subjected to further heat treatment,including (but not limited to) calcination, annealing, nitriding andreduction. The heat treatment step(s) may be performed before the activemetal precursor is applied to the surface of the doped support. The heattreatment step(s) may also be performed before the promoter precursor isapplied to the surface of the doped support, in which case the dryingstep(s) and the heat treatment step(s) may need to be repeated beforethe active metal precursor is applied to the surface of the dopedsupport.

Calcination of the Support or Doped Support

The chemical composition of the surface of the support or doped supportcan be modified, or thermally activated, to further improve thecharacteristics and properties of the catalyst. Such modifications maybe used to improve or moderate the dispersion of active metal species,and/or the surface morphology, selectivity, activity, or temperaturesensitivity of the catalyst. One such modification is calcination, whichis performed at elevated temperatures, with the objective of convertingup to 100% of the precursor species on the surface to the metal oxidesor mixed metal oxides. The elevated temperatures may also be selected topromote solid state reaction(s) between the catalyst support materialand/or the metal dopants and/or promoters to form solid solutions oralloys which further improve the desired characteristics and performanceof the final catalyst. An oxidizing or inert (i.e. non-reducing)atmosphere, e.g. comprising air, N₂, CO₂, Ar, He, Xe (or mixturesthereof), may be used. Once the high temperature heat treatment hasreached the end of the desired time duration, the nitrided materialremains in the oven and in the same atmosphere, and it is allowed tocool to ambient temperature over a period of several hours. If a flowingor circulating atmosphere is used, then the time for effective heattreatment at high temperatures may be reduced significant (e.g. between2 to 6 hours at temperatures from 500° C. to 1000° C.).

In some embodiments, the support or doped support may be maintained at atemperature of at least about 300, 350, 400, 450, 500, 550, 600, 650,700, 750, 800, 850, 900, 950, 1000, 1050, 1100, 1150, 1200, or 1250° C.,for a duration of about 0.1 to about 168 hours, in an oxidizing (e.g.,an environment comprising at least oxygen) or inert atmosphere. In someembodiments, the support or doped support may be maintained at atemperature of not more than about 350, 400, 450, 500, 550, 600, 650,700, 750, 800, 850, 900, 950, 1000, 1050, 1100, 1150, 1200, 1250, or1300° C., for a duration of about 0.1 to about 168 hours, in anoxidizing or inert atmosphere.

In some instances, the support or doped support may be maintained at atemperature of about 300° C. to about 1300° C., fora duration of atleast about 0.1, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35,40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, 115, 120,132, 144, or 156 hours, in an oxidizing or inert atmosphere. In someinstances, the support or doped support may be maintained at atemperature of about 300° C. to about 1300° C., for a duration of notmore than about 0.1, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30,35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, 115,120, 132, 144, 156, or 168 hours, in an oxidizing or inert atmosphere.

Annealing of the Support or Doped Support

The chemical composition of the surface of the support or doped supportcan be modified, or thermally activated, to further improve thecharacteristics and properties of the catalyst. Such modifications maybe used to improve or moderate the dispersion of active metal species,and/or the surface morphology, selectivity, activity, or temperaturesensitivity of the catalyst. One such modification is annealing, whichis performed at elevated temperatures, with the objective of modifyingthe crystal structure, and/or size and/or composition of the surfacelayers. In some embodiments, annealing may be performed to agglomeratesmaller particles to combine into larger particles and expose a largerarea of the surface support or doped support. In some instances,annealing may be performed to partially reduce the support, or dopedsupport. In some instances, annealing may be performed to generateoxygen vacancies in the support, or doped support. The elevatedtemperatures may also be selected to promote solid state reaction(s)between the catalyst support material and/or the metal dopants and/orpromoters to form solid solutions or alloys which further improve thedesired characteristics and performance of the final catalyst. An inert,anoxic, or non-oxidizing atmosphere, e.g., comprising any of N₂, CO₂,CO, H₂, Ar, He, Kr, Xe (or mixtures thereof), may be used. Once the hightemperature heat treatment has reached the end of the desired timeduration, the nitrided material remains in the oven and in the sameatmosphere, and it is allowed to cool to ambient temperature over aperiod of several hours. If a flowing or circulating atmosphere is used,then the time for effective heat treatment at high temperatures may bereduced significant (e.g. between 2 to 6 hours at temperatures from 500°C. to 1000° C.).

In some embodiments, the support or doped support may be maintained at atemperature of at least about 300, 350, 400, 450, 500, 550, 600, 650,700, 750, 800, 850, 900, 950, 1000, 1050, 1100, 1150, 1200, or 1250° C.,for a duration of about 0.1 to about 168 hours, in an inert, anoxic orreducing atmosphere. In some embodiments, the support or doped supportmay be maintained at a temperature of not more than about 350, 400, 450,500, 550, 600, 650, 700, 750, 800, 850, 900, 950, 1000, 1050, 1100,1150, 1200, 1250, or 1300° C., for a duration of about 0.1 to about 168hours, in an inert, anoxic or reducing atmosphere.

In some embodiments, the support or doped support may be maintained at atemperature of about 300° C. to about 1300° C., for a duration of atleast about 0.1, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35,40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 100, 105, 110, 115,120, 132, 144, or 156 hours, in an inert, anoxic or reducing atmosphere.In some embodiments, the support or doped support may be maintained at atemperature of about 300° C. to about 1300° C., for a duration of notmore than about 0.1, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30,35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, 115,120, 132, 144, 156, or 168 hours, in an inert, anoxic or reducingatmosphere.

Nitriding of the Support or Doped Support

The chemical composition of the surface of the support or doped supportcan be modified, or thermally activated, to further improve thecharacteristics of the catalyst. Such modifications may be used toimprove or moderate the dispersion of active metal species, and/or thesurface morphology, selectivity, activity, or temperature sensitivity ofthe catalyst. One such modification is nitriding, which is performed atelevated temperatures, with the objective of converting up to 100% ofthe metal oxides or precursor species on the surface to the metalnitrides. The elevated temperatures may also be selected to promotesolid state reaction(s) between the catalyst support material and/or themetal dopants and/or promoters to form solid solutions or alloys whichfurther improve the desired characteristics and performance of the finalcatalyst. A reactive, nitrogen-rich or nitrogen-containing atmospherecomprising e.g. NH₃, H₂—N₂, forming gas, or endothermic gas (or mixturesthereof), may be used. Once the high temperature heat treatment hasreached the end of the desired time duration, the nitrided materialremains in the oven and in the same atmosphere, and it is allowed tocool to ambient temperature over a period of several hours. If a flowingor circulating atmosphere is used, then the time for effective heattreatment at high temperatures may be reduced significant (e.g. between2 to 6 hours at temperatures from 500° C. to 1000° C.).

In some embodiments, the support or doped support may be maintained at atemperature of at least about 300, 350, 400, 450, 500, 550, 600, 650,700, 750, 800, 850, 900, 950, 1000, 1050, 1100, 1150, 1200, or 1250° C.,for a duration of about 0.1 to about 168 hours, in a reactive,nitrogen-rich or nitrogen-containing atmosphere. In some embodiments,the support or doped support may be maintained at a temperature of notmore than about 350, 400, 450, 500, 550, 600, 650, 700, 750, 800, 850,900, 950, 1000, 1050, 1100, 1150, 1200, 1250, or 1300° C., for aduration of about 0.1 to about 168 hours, in a reactive, nitrogen-richor nitrogen-containing atmosphere.

In some embodiments, the support or doped support may be maintained at atemperature of about 300° C. to about 1300° C., for a duration of atleast about 0.1, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35,40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, 115, 120,132, 144, or 156 hours, in a reactive, nitrogen-rich ornitrogen-containing atmosphere. In some embodiments, the support ordoped support may be maintained at a temperature of about 300° C. toabout 1300° C., for a duration of not more than about 0.1, 0.5, 1, 2, 3,4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70,75, 80, 85, 90, 95, 100, 105, 110, 115, 120, 132, 144, 156, or 168hours, in a reactive, nitrogen-rich or nitrogen-containing atmosphere.

Reduction of the Support or Doped Support

As discussed above, once the active metal (e.g. Ru) precursor isdeposited on the carrier or support (e.g. alumina, doped or modifiedalumina), reduction of the precursor may lead to an improved activemetal nanoparticle catalyst that can be used to facilitate ammoniadecomposition. The conditions of such reduction may strongly influencethe physical or chemical properties or characteristics of the activemetal on the surface of the support, and thus the activity and/orammonia conversion efficiency of the catalyst. Furthermore, theconditions of reduction may strongly influence properties of the activemetal nanoparticles on the surface, including, for example, size,dispersion and dominant crystal facets. In some cases, the reduction ofthe precursor(s) may be performed in an atmosphere comprising hydrogen.Once the high temperature heat treatment has reached the end of thedesired time duration, the nitrided material remains in the oven and inthe same atmosphere, and it is allowed to cool to ambient temperatureover a period of several hours. When performed under ideal conditions,the heat treatment step under these conditions may be conducted for aperiod from 2 hours to 6 hours.

In some embodiments, the doped support may be maintained at atemperature of at least about 200, 250, 300, 350, 400, 450, 500, 550,600, 650, 700, 750, 800, 850, 900, 950, 1000, 1050, 1100, 1150, 1200, or1250° C., for a duration of about 0.1 hours to about 168 hours, in anatmosphere comprising hydrogen. In some embodiments, the doped supportmay be maintained at a temperature of not more than about 250, 300, 350,400, 450, 500, 550, 600, 650, 700, 750, 800, 850, 900, 950, 1000, 1050,1100, 1150, 1200, 1250, or 1300° C., for a duration of 0.1 hour to about168 hours, in an atmosphere comprising hydrogen.

In some embodiments, the support or doped support may be maintained at atemperature of about 200° C. to about 1300° C., for a duration of atleast about 0.1, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35,40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, 115, 120,132, 144, or 156 hours, in an atmosphere comprising hydrogen. In someembodiments, the support or doped support may be maintained at atemperature from about 200° C. to about 1300° C., for a duration of notmore than about 0.1, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30,35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, 115,120, 132, 144, 156, or 168 hours, in an atmosphere comprising hydrogen.

Effect of Reduction Temperature

As discussed above, once the ruthenium precursor is deposited on thealumina carrier or support, reduction of the precursor may lead to animproved ruthenium nanoparticle catalyst that can be used to facilitateammonia decomposition. The conditions of such reduction may stronglyinfluence the physical or chemical properties or characteristics of theruthenium on the surface of the support, and thus the activity and/orammonia conversion efficiency of the catalyst. Surprisingly, theconditions of reduction may strongly influence properties of theruthenium nanoparticles on the surface, including, for example, size,dispersion and dominant crystal facets.

Described herein is an example that reduction at a higher temperaturemay surprisingly result in improved ammonia conversion performanceacross a wide temperature range (from about 400° C. to about 550° C.),even for a more effective, doped catalyst. With reference to FIG. 9 , aRu/La-gamma-alumina catalyst may be prepared according to the methodsand materials described herein, and reduced for a set period of time ina H₂ atmosphere, at a temperature of about 900° C. 901, or about 500° C.902.

In some instances, the catalyst reduction temperature may range fromabout 500 to about 1300, from about 550 to about 1250, from about 600 toabout 1200, from about 650 to about 1150, from about 700 to about 1100,from about 750 to about 1050, from about 800 to about 1000, or fromabout 850 to about 950° C. In some cases, the catalyst reduction periodmay range from about 0.5 hour to about 200 hours, from about 1 hour toabout 190 hours, from about 5 hours to about 180 hours, or from about 10hours to about 170 hours, from about 15 hours to about 160 hours, fromabout 20 hours to about 150 hours, from about 25 hours to about 140hours, or from about 30 hours to about 130 hours, from about 35 hours toabout 120 hours, from about 40 hours to about 110 hours, from about 45hours to about 100 hours, or from about 50 hours to about 95 hours, fromabout 55 hours to about 90 hours, from about 60 hours to about 85 hours,from about 65 hours to about 80 hours, or from about 70 hours to about75 hours.

Alumina Support Phase

While gamma-alumina is an alumina phase that is commonly used as acatalyst support, other phases of alumina exist, including alpha, theta,delta and eta. Alpha alumina (α-Al₂O₃) can be provided in a highlysintered form of the support with a very low surface area, which canlead to poor catalyst dispersion. In contrast, theta alumina (θ-Al₂O₃)can be a phase that is generated during the transition from gamma toalpha at very high temperatures and can retain a relatively high surfacearea, which can make theta alumina one example of a higher performingsupport material.

Described herein is an example that the unexpected effect of usingtheta-alumina (θ-alumina) as the support material compared to usinggamma-alumina (γ-alumina). Across a temperature range from about 400° C.to about 550° C., the catalyst using 1.6 mm beads of theta-aluminaexhibited equivalent performance to the catalyst using 1.0 mm beads ofgamma-alumina. Across a temperature range from about 400° C. to about525° C., the catalyst using 1.6 mm beads of gamma-alumina gave inferiorperformance to the other two catalysts. It is surprising to observeimproved performance using theta-alumina compared to higher porositygamma-alumina, but these results indicate that larger form factors canbe used with theta-alumina, reducing the pressure drop across thecatalyst bed while maintaining conversion performance.

With reference to FIG. 10 , Ru-alumina catalysts may be preparedaccording to the same methods and materials (described herein) and withthe same composition. The catalysts may use 1.6 mm beads comprised oftheta-alumina 1001, 1.0 mm beads comprised of gamma-alumina 1002, or 1.6mm beads comprised of gamma-alumina 1003.

In some cases, in a full-scale reformer, pressure drops may besignificant and may be a function of the size of the support used, andas the particles get smaller, the pressure drop may increase. In somecases, switching the phase of the support from gamma-alumina totheta-alumina may allow the catalyst to perform comparably to smallercatalysts, while still minimizing pressure drop with a larger catalystsize. In some embodiments, the support comprises at least one oftheta-alumina (θ-Al₂O₃) or gamma-alumina (γ-Al₂O₃). In some embodiments,the support comprises theta-alumina (θ-Al₂O₃). In some embodiments, thesupport comprises gamma-alumina (γ-Al₂O₃).

Effect of Ru Precursor

Described herein is an example of the unexpected effect of the choice ofRu precursor. In some cases, the ruthenium nanoparticle catalysts of thepresent disclosure may be synthesized using various ruthenium precursorscomprising, for example, Ru(NO)(NO₃)₃, RuCl₃ and Ru₃(CO)₁₂.

The use of Ru(NO)(NO₃)₃ resulted in improved catalyst performance acrossa wide temperature range (from about 400° C. to about 525° C.). The useof RuCl₃ gave lower performance and Ru₃(CO)₁₂ provided the lowestperformance in a temperature range from about 400° C. to about 600° C.With respect to FIG. 10 , Ru-alumina catalysts with 2 wt % Ru contentand having the same final composition may be prepared by the same methodand materials, described herein. The catalysts may be prepared using aRu precursor comprising: Ru(NO)(NO₃)₃ 1001, RuCl₃ 1002, or Ru₄(CO)₁₂1003.

Mixed La—Al, Ce—Al, and La—Ce—Al Oxide Supports

In some cases, the alumina support may be initially modified byincorporation of lanthanum via high-temperature calcination to generatea La—Al oxide support that can serve as an improved catalyst support.

The catalysts described in this disclosure were prepared by the wetimpregnation method, as described herein. Other synthesis techniques(e.g. sol-gel, precipitation, CVD) may also be used to prepare thesecatalysts. In some embodiments, the catalyst may be prepared by doping asupport material with at least one precursor comprising La. In someembodiments, the catalyst may be prepared by doping a support materialwith at least one precursor comprising Ce. In some instances, thecatalyst may be prepared by doping a support material with at least oneprecursor comprising Cs. In some instances, the catalyst may be preparedby doping a support material with at least one precursor comprising Laand Ce. In some embodiments, the catalyst may be prepared by doping asupport material with at least one precursor comprising La, Ce and Cs.

In some instances, this may be achieved by using suitable precursors,for example, La(NO₃)₃, Ce(NO₃)₃, CsNO₃, and their hydrates. In someinstances, the La and Ce precursors may be applied as one solution(using deionized water, or other suitable solvent), or separately. Insome embodiments, the Cs precursor may be applied as a separatesolution. In some instances, each precursor may be applied as a separatesolution, with a drying step between each application, (as describedherein). In some embodiments, the Ce precursor may be applied to thesupport material before the La precursor. In some embodiments, the Laprecursor may be applied to the support material before the Ceprecursor.

The concentration of the precursor solutions is determined by thedesired metal loading on the catalyst. In some embodiments, it may beconvenient to use the desired loading of La on the catalyst as the basisfor the concentrations of the precursor solution(s). In someembodiments, it may be convenient to use the desired loading of Ce asthe basis for the concentrations of precursor solution(s). Therelationships between catalyst loading, the required concentrations ofthe precursor solutions and their preparation are described herein.

Incorporation of La

Described herein is an example of the surprising improvement in ammoniaconversion efficiency that may be achieved with the use of theta-aluminasupport material doped with lanthanum (La), the use of a more effectivemolar ratio of active metal and promoter, and the selection ofappropriate reduction conditions.

With respect to FIG. 12 , Ru-alumina catalysts may be prepared with thesame concentration of Ru and a constant dopant level of La, according tothe same methods and materials described herein, and using the same formfactor for the support materials. Gamma-alumina (γ-alumina) may be usedfor the support material (1201 and 1202) or theta-alumina (θ-alumina)may be used (1203, 1204, and 1205). The catalyst may not comprise apromoter 1201, 1203 and 1204, or it may comprise a promoter (Cs) 1202and 1205. The catalyst may not be subjected to a heat treatment step1201 and 1202, The catalyst may be subjected to a high temperaturereduction step in a H₂ atmosphere, for a duration of about 2 hours 1203and 1205, or for about 12 hours 1204.

In some embodiments, the concentration of La in the catalyst maycomprise at least about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14,15, 16, 17, 18, 19, 20, 21, 22, 23, or 24 mol %. In some embodiments,the concentration of La in the catalyst may comprise not more than about2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21,22, 23, 24, or 25 mol %. In some embodiments, the concentration of La inthe catalyst may comprise from about 1 to about 15, about 1 to about 10,about 1 to about 5, about 2 to about 8, about 2 to about 6, about 2 toabout 4, about 4 to about 10, about 4 to about 8, about 4 to about 6,about 5 to about 20, about 5 to about 15, about 5 to about 10, about 6to about 10, about 6 to about 8, about 8 to about 10, about 10 to about20, about 10 to about 18, about 10 to about 16, about 10 to about 14,about 10 to about 12, about 15 to about 20, about 12 to about 18, about12 to about 16, about 12 to about 14, about 14 to about 20, about 14 toabout 18, about 14 to about 16, about 16 to about 18, or about 18 toabout 20 mol %

Incorporation of La with Ce

Described herein is an example of the unexpected synergy between La andCe to give improved catalyst performance beyond that demonstrated byeach dopant alone, while maintaining a constant total dopant metalconcentration of 15 mol %. With respect to FIG. 13 , Ru-aluminacatalysts may be prepared according to the methods and materialsdescribed herein, and based on the same form factor for the support. Thecatalyst may be doped with La 1301, the catalyst may be doped with Ce1302, or the catalyst may be doped with a of La and Ce combined 1303.

In some instances, it may be convenient to determine the requiredconcentration of Ce in the catalyst by the concentration of La and thedesired molar ratio of La and Ce. In some instances, it may beconvenient to determine the required concentration of La in the catalystby the concentration of Ce and the desired molar ratio of Ce and La.

In some embodiments, the concentration of Ce in the catalyst maycomprise at least about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14,15, 16, 17, 18, 19, 20, 21, 22, 23, or 24 mol %. In some embodiments,the concentration of Ce in the catalyst may comprise no more than about2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21,22, 23, 24 or 25 mol %. In some embodiments, the concentration of Ce inthe catalyst may comprise from about 1 to about 25, about 1 to about 15,about 1 to about 5, about 2 to about 8, about 2 to about 6, about 2 toabout 4, about 4 to about 10, about 4 to about 8, about 4 to about 6,about 5 to about 20, about 5 to about 15, about 5 to about 10, about 6to about 10, about 6 to about 8, about 8 to about 10, about 10 to about20, about 10 to about 18, about 10 to about 16, about 10 to about 14,about 10 to about 12, about 15 to about 20, about 12 to about 18, about12 to about 16, about 12 to about 14, about 14 to about 20, about 14 toabout 18, about 14 to about 16, about 16 to about 18, or about 18 toabout 20 mol %

In some embodiments, the combined concentration of La and Ce in thecatalyst may comprise at least about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11,12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, or 24 mol %. In someembodiments, the combined concentration of La and Ce in the catalyst maycomprise no more than about 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14,15, 16, 17, 18, 19, 20, 21, 22, 23, 24 or 25 mol %. In some embodiments,the combined concentration of La and Ce in the catalyst may comprisefrom about 1 to about 15, about 1 to about 10, about 1 to about 5, about2 to about 8, about 2 to about 6, about 2 to about 4, about 4 to about10, about 4 to about 8, about 4 to about 6, about 5 to about 20, about 5to about 15, about 5 to about 10, about 6 to about 10, about 6 to about8, about 8 to about 10, about 10 to about 20, about 10 to about 18,about 10 to about 16, about 10 to about 14, about 10 to about 12, about15 to about 20, about 12 to about 18, about 12 to about 16, about 12 toabout 14, about 14 to about 20, about 14 to about 18, about 14 to about16, about 16 to about 18, or about 18 to about 20 mol %.

High Temperature Treatment to Form Modified Surface Layer

In some cases, the conditions of the high temperature treatment may beselected to improve the solid-state reaction between the alumina (Al₂O₃)support and cerium oxide (CeO₂) and lanthanum oxide (La₂O₃) dopants (orprecursors) on the support surface. In some instances, this reactionresults in the formation of a surface layer comprised of a perovskitephase, comprising of Al, O, and La. In some instances, this reactionresults in the formation of a surface layer comprised of a perovskitephase, comprising of Al, O, and Ce. In some embodiments, this reactionresults in the formation of a surface layer comprised of a perovskitephase, comprising of Al, O, La, and Ce. In some instances, theperovskite phase may comprise a continuous matrix of mixed metal oxides(La:Ce)AlO_(x), wherein the metals are dispersed homogeneouslythroughout the matrix. In some instances, the perovskite phase maycomprise a non-continuous matrix of mixed metal oxides (La:Ce)AlO_(x),where the metals are dispersed homogenously throughout the matrix. Insome cases, the perovskite phase may comprise a continuous matrix ofmixed metal oxides, wherein the metals are not dispersed homogeneouslythroughout the matrix. In some cases, the perovskite phase may comprisea non-continuous matrix of mixed metal oxides, where the metals are notdispersed homogenously throughout the matrix. In some cases, theperovskite phase may comprise one or more repeating unit cells spanninga lattice, where each unit cell comprises lanthanum, cerium, aluminumand oxygen. In some cases, the surface layer comprises theta-alumina(θ-alumina). In some cases, the surface layer comprises gamma-alumina(α-alumina).

In some embodiments, doping of a La—Al oxide support with anelectron-donating metal such as cerium may comprise La—Ce—Al oxidesupports of the general formula La_((1-x))Ce_(x)AlO₃/Al₂O₃. In someinstances, the La_((1-x))Ce_(x)AlO₃/Al₂O₃ composition may comprise, forexample, a mixed La—Ce oxide structure. In some embodiments, the surfacelayer comprises a perovskite phase of the general formulaLa_((1-x))Ce_(x)AlO₃. The value of x in this formula may be at leastabout 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, or 0.9. The value of x inthis formula may be no more than about 0.2, 0.3, 0.4, 0.5, 0.6, 0.7,0.8, 0.9, or 0.95. The value of x may be from about 0.05 to about 0.9,from about 0.1 to about 0.7, from about 0.15 to about 0.5, from about0.2 to about 0.4, or from about 0.25 to about 0.35.

Incorporation of Cs and Ru

In some cases, it may be convenient to determine the requiredconcentration of Cs in the catalyst by the desired molar ratio of Cs andRu, and the desired concentration of Ru in the catalyst. In some cases,it may be convenient to determine the required concentration of Ru inthe catalyst by the desired molar ratio of Ru and Cs, and the desiredconcentration of Cs in the catalyst.

In some instances, the doped and calcined support is further doped withCs. In some embodiments, the concentration of Cs in the catalyst maycomprise at least about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14,15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32,33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50,51, 52, 53, 54, 55, 56, 57, 58, or 59 wt %. In some embodiments, theconcentration of Cs in the catalyst may comprise not more than about 1,2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21,22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39,40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57,58, 59, or 60 wt %. In some embodiments, the concentration of Cs in thecatalyst may comprise from about 1 to about 15, about 1 to about 10,about 1 to about 5, about 2 to about 8, about 2 to about 6, about 2 toabout 4, about 4 to about 10, about 4 to about 8, about 4 to about 6,about 5 to about 20, about 5 to about 15, about 5 to about 10, about 6to about 10, about 6 to about 8, about 8 to about 10, about 10 to about20, about 10 to about 18, about 10 to about 16, about 10 to about 14,about 10 to about 12, about 15 to about 20, about 12 to about 18, about12 to about 16, about 12 to about 14, about 14 to about 20, about 14 toabout 18, about 14 to about 16, about 16 to about 18, or about 18 toabout 20 wt %.

In some embodiments, the doped and calcined support is further dopedwith Ru. In some embodiments, the concentration of Ru in the catalystmay comprise at least about 0.1, 0.25, 0.5, 0.75, 1, 1.25, 1.5, 2, 2.5,3, 3.5, 4, 4.5, 5, 6, 7, 8, 9, 10, 11, 12, 13, or 14 wt %. In someembodiments, the concentration of Ru in the catalyst may comprise nomore than about 0.25, 0.5, 0.75, 1, 1.25, 1.5, 2, 2.5, 3, 3.5, 4, 4.5,5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15 wt %. In some embodiments, theconcentration of Ru in the catalyst may comprise from about 1 to about15, about 1 to about 10, about 1 to about 5, about 1 to about 3, about 2to about 8, about 2 to about 6, about 2 to about 4, about 3 to about 5,about 4 to about 10, about 4 to about 8, about 4 to about 6, about 5 toabout 10, about 5 to about 7, about 6 to about 10, about 6 to about 8,about 7 to about 9, or about 8 to about 10 mol %.

In some embodiments, the molar ratio of K or Cs and Ru may comprise atleast about 1:2, 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, 5:1,5.5:1, 6:1, 7:1, 8:1, or 9:1. In some embodiments, the molar ratio of Kor Cs and Ru may comprise no more than about 1:1, 1.5:1, 2:1, 2.5:1,3:1, 3.5:1, 4:1, 4.5:1, 5:1, 5.5:1, 6:1, 7:1, 8:1, 9:1, or 10:1. In someinstances, the molar ratio of K or Cs and Ru may comprise from about 1:2to about 5.5:1, from about 1:1 to about 5:1, from about 1.5:1 to about4.5:1, from about 2:1 to about 4:1, or from about 2.5:1 to about 3.5:1.

Mixed La—Ce—Al Oxide Support and Cs Promotion for Theta Alumina

Referring to FIG. 14 and FIG. 15 , in some cases, the catalysts of thepresent disclosure may be further improved by adjusting the molar ratioof La and Ce.

Described herein is an example showing that the unexpected synergybetween La and Ce (according to the formula,Ru—Cs/La_(1-x)Ce_(x)-Theta-Al₂O₃) is most effective when the value of xis greater than 0 and less than 0.5 With respect to FIG. 14 , Ru-aluminacatalysts may be prepared according to the methods and materialsdescribed herein, based on theta-alumina (θ-alumina) and the same formfactor for the support. The catalysts may comprise the sameconcentration of active metal (Ru), the same molar ratio of Ru andpromoter (Cs), and different ratios of La and Ce dopants at a constantcombined dopant loading, according to the formula:Ru—Cs/La_(1-x)Ce_(x)-Theta-Al₂O₃. The catalysts may comprise values forx of: x=0 (no Ce) 1401, x=0.1 1402, x=0.3 1403, or x=0.5 1404. Theconversion efficiency of these catalysts was measured at a fixedtemperature and fixed NH₃ flow rate.

Described herein is an example showing that unexpected synergy betweenLa and Ce is observed across a wide temperature range (about 400° C. toabout 550° C.), in the same ratios as used in Example 9. With respect toFIG. 15 , Ru-alumina catalysts may be prepared with constant Ruconcentration according to the methods and materials described herein,based on theta-alumina (θ-alumina) and the same form factor for thesupport. The catalysts may comprise Ru/La_((1-x))Ce_(x)-Theta-Al₂O₃ withvalues for x of: x=0 (no Ce) 1501, x=0.1 1502, x=0.3 1503, or x=0.51504. The conversion efficiency of these catalysts may be measuredacross a temperature range and at constant NH₃ flow rate.

Such further improvements may yield a catalyst that exhibits enhancedperformance characteristics compared to other catalysts fabricated usingvarious baseline conditions. In some examples, the baseline conditionsmay correspond to an incorporation amount of Ru, a molar ratio of Cspromoter to Ru, a type of Ru precursor, a catalyst reductiontemperature, a catalyst reduction period and alumina support phase. Inany of the embodiments described herein, the alumina support phase maybe theta-alumina, gamma-alumina, or a combination of both. In someembodiments, a mixed La—Ce—Al oxide structure may be introduced on or toa support comprising theta alumina by varying a molar ratio of La andCe, as shown in FIG. 14 and FIG. 15 . In some embodiments, the molarratio of La and Ce may be at least about 95:5, 90:10, 85:15, 80:20,75:25, 70:30, 65:35, 60:40, 55:45, 50:50, 45:55, 40:60, 35:65, 30:70,25:75, 20:80, 15:85, 10:90, 5:95, or 0:100. In some embodiments, themolar ratio of La and Ce may be at least about 100:0, 95:5, 90:10,85:15, 80:20, 75:25, 70:30, 65:35, 60:40, 55:45, 50:50, 45:55, 40:60,35:65, 30:70, 25:75, 20:80, 15:85, 10:90, or 5:95. In some embodiments,the molar ratio of La and Ce may be not more than about 100:0, 95:5,90:10, 85:15, 80:20, 75:25, 70:30, 65:35, 60:40, 55:45, 50:50, 45:55,40:60, 35:65, 30:70, 25:75, 20:80, 15:85, 10:90, or 5:95. In someembodiments, the molar ratio of La and Ce may range from about 100:0 toabout 0:100, 100:0 to 90:10, 100:0 to 80:20, 100:0 to 70:30, 100:0 to60:40, 100:0 to 50:50, 90:10 to 10:90, 90:10 to 80:20, 90:10 to 70:30,90:10 to 60:40, 90:10 to 50:50, 80:20 to 70:30, 80:20 to 60:40, 80:20 to50:50, 75:25, to 70:30, 75:25 to 65:35, 75:25 to 60:40, 75:25 to 55:45,75:25 to 50:50, 75:25 to 40:60, 70:30 to 65:35, 70:30 to 60:40, 70:30 to55:45, 70:30 to 50:50, 70:30 to 40:60, 65:35 to 60:40, 65:35 to 55:45,65:35 to 50:50, 65:35 to 40:60, 60:40 to 50:50, or 60:40 to 40:60. Insome cases, there may be an upward trend in activity or ammoniaconversion efficiency as a function of cerium content in the support.

Ammonia Reforming System

FIG. 16 is block diagram illustrating an ammonia reforming system 2000,in accordance with one or more embodiments of the present disclosure.The ammonia reforming system 2000 comprises an NH₃ storage tank 2002, aheat exchanger 2006, one or more combustion-heated reformers 2008, acombustion heater 2009, one or more electrically-heated reformers 2010,an electric heater 2011, an air supply unit 2016, an ammonia filter2022, and a hydrogen processing module 2024. The ammonia reformingsystem is described in more detail in U.S. patent application Ser. No.17/974,885, which is incorporated herein by reference in its entiretyfor all purposes.

The NH₃ storage tank 2002 may be configured to store NH₃ under pressure(e.g., 7-9 bars absolute) and/or at a low temperature (e.g., −30° C.).The NH₃ storage tank 2002 may comprise a metallic material that isresistant to corrosion by ammonia (e.g., steel). The storage tank 2002may comprise one or more insulating layers (e.g., perlite or glasswool). In some cases, an additional heater may be positioned near,adjacent, at, or inside the NH₃ storage tank 2002 to heat and/orpressurize the NH₃ stored therein.

The heat exchanger 2006 may be configured to exchange heat betweenvarious input fluid streams and output fluid streams. For example, theheat exchanger 2006 may be configured to exchange heat between anincoming ammonia stream 2004 provided by the storage tank 2002 (e.g.,relatively cold liquid ammonia) and a reformate stream 2020 (e.g., arelatively warm H₂/N₂ mixture) provided by the reformers 2008 and 2010.The heat exchanger 2006 may be a plate heat exchanger, a shell-and-tubeheat exchanger, or a tube-in-tube heat exchanger, although the presentdisclosure is not limited thereto.

The reformers 2008 and 2010 may be configured to generate and output thereformate stream 2020 comprising at least a mixture of hydrogen (H₂) andnitrogen (N₂) (with a molar ratio of H₂ to N₂ of about 3:1 at a highammonia conversion). The H₂/N₂ mixture may be generated by contactingthe incoming ammonia stream 2004 with NH₃ reforming catalyst positionedinside each of the reformers 2008 and 2010. The reformers 2008 and 2010may be heated to a sufficient temperature range to facilitate ammoniareforming (for example, of from about 400° C. to about 650° C.).

In some embodiments, the reformers 2008 and 2010 may comprise aplurality of reformers, which may fluidically communicate in variousseries and/or parallel arrangements. For example, an electrically-heatedreformer 2010 may fluidically communicate in series or in parallel witha combustion-heated reformer 2008 (or vice versa) as a pair of reformers2008-2010. Such a pair of reformers 2008-2010 may fluidicallycommunicate in parallel with other reformer 2008-2010 or pairs ofreformers 2008-2010 (so that pairs of reformers 2008-2010 combine theiroutputs into a single reformate stream 2020), or may fluidicallycommunicate in series with other reformers 2008-2010 or pairs ofreformers 2008-2010.

In some embodiments, the number of combustion-heated reformers 2008 maybe the same as the number of electrically-heated reformers 2010, and thereformers 2008-2010 may fluidically communicate in various series and/orparallel arrangements. For example, two electrically-heated reformers2010 may fluidically communicate in series with two combustion-heatedreformers 2008 (or vice versa).

In some embodiments, the number of combustion-heated reformers 2008 maybe different from the number of electrically-heated reformers 2010 andthe reformers 2008-2010 may fluidically communicate in various seriesand/or parallel arrangements. For example, two electrically-heatedreformers 2010 may fluidically communicate in series with fourcombustion-heated reformers 2008 (or vice versa).

The combustion heater 2009 may be in thermal communication with thecombustion-heated reformer 2008 to heat the NH₃ reforming catalyst 2030in the reformer 2008. The combustion heater 2009 may react at least partof the reformate stream 2020 (e.g., the H₂ in the H₂/N₂ mixture) with anair stream 2018 (e.g., at least oxygen (O₂)). The heat from theexothermic combustion reaction in the combustion heater 2009 may betransferred to the NH₃ reforming catalyst 2030 in the reformer 2008. Forexample, the hot combustion product gas 2014 may contact walls of thereformer 2008, and the hot combustion product gas 2014 may besubsequently output from the combustion heater 2009 as combustionexhaust 2014. The combustion heater 2009 may comprise a separatecomponent from the reformer 2008 (and may be slidably insertable orremovable in the reformer 2008). In some cases, the combustion heater2009 is a unitary structure with the combustion-heated reformer 2008(and both the reformer 2008 and the heater 2009 may be manufactured via3D printing and/or casting).

The air supply unit 2016 (e.g., one or more pumps and/or compressors)may be configured to supply the air stream 2018 (which may be sourcedfrom the atmosphere, and may comprise at least about 20% oxygen by molarfraction). The air stream 2018 may comprise pure oxygen by molarfraction, or substantially pure oxygen by molar fraction (e.g., at leastabout 99% pure oxygen).

The electric heater 2011 may be in thermal communication with theelectrically-heated reformer 2010 to heat the NH₃ reforming catalyst2030 in the reformer 2010. The electric heater 2011 may heat the NH₃reforming catalyst 2030 in the electrically-heated reformer 2010 byresistive heating or Joule heating. In some cases, the electrical heater2011 may comprise at least a heating element (e.g., nichrome or ceramic)that transfers heat to the catalyst 2030 in the electrically-heatedreformer 2010. In some cases, the electrical heater 2011 may comprisemetal electrodes (e.g., copper or steel electrodes) that pass a currentthrough the catalyst 2030 to heat the catalyst 2030 in the reformer2010.

The ammonia filter 2022 may be configured to filter or remove traceammonia in the reformate stream 2020. The ammonia filter 2022 may beconfigured to reduce the concentration of NH₃ in the reformate stream2020, for example, from greater than about 10,000 parts per million(ppm) to less than about 100 ppm. The ammonia filter 2022 may comprise afluidized bed comprising a plurality of particles or pellets. Theammonia filter 2022 may be cartridge-based (for simple replaceability,for example, after the ammonia filter 2022 is saturated with ammonia).

The ammonia filter 2022 may comprise an adsorbent (e.g., bentonite,zeolite, clay, biochar, activated carbon, silica gel, metal organicframeworks (MOFs), and other nanostructured materials). The adsorbentmay comprise pellets, and may be stored in one or more columns ortowers. In some instances, the ammonia filter 2022 may comprise anabsorbent, a solvent-based material, and/or a chemical solvent.

In some embodiments, the ammonia filter 2022 comprises a multi-stageammonia filtration system (e.g., water-based) comprising a plurality offiltration stages. The replacement of water-based absorbents may beperformed for continuous operation.

In some embodiments, the ammonia filter 2022 comprises a selectiveammonia oxidation (SAO) reactor including oxidation catalysts configuredto react the trace ammonia in the reformate stream 2020 with oxygen (O₂)to generate nitrogen (N₂) and water (H₂O). The air stream 2018 (or aseparate oxygen source) may be provided to the SAO reactor to providethe oxygen for the oxidation reaction.

In some embodiments, the ammonia filter 2022 may comprise an acidicammonia remover (for example, in addition to adsorbents), which mayinclude an acidic solid or solution. The acidic ammonia remover may beregenerated (to desorb the ammonia captured therein) by passing anelectric current through the acidic ammonia remover.

The hydrogen processing module 2024 may be a fuel cell comprising ananode, a cathode, and an electrolyte between the anode and the cathode.The fuel cell 2024 may comprise a polymer electrolyte membrane fuel cell(PEMFC), a solid oxide fuel cell (SOFC), a molten carbonate fuel cell(MCFC), a phosphoric acid fuel cell (PAFC), or an alkaline fuel cell(AFC), although the present disclosure is not limited thereto. The fuelcell 2024 may process the H₂ in the reformate stream 2020 at an anode,and process the 02 in the air stream at a cathode, to generateelectricity (to power an external electrical load). The fuel cell 2024may be configured to receive hydrogen (e.g., at least part of thereformate stream 2020) via one or more anode inlets, and oxygen (e.g.,at least part of the air stream 2018 or a separate air stream) via oneor more cathode inlets.

In some embodiments, the fuel cell 2024 may output unconsumed hydrogen(e.g., as an anode off-gas) via one or more anode outlets, and/or mayoutput unconsumed oxygen (e.g., as a cathode off-gas) via one or morecathode outlets. The anode off-gas and/or the cathode off-gas may beprovided to the combustion heater 2009 as reactants for the combustionreaction performed therein.

The storage tank 2002 may be in fluid communication with thecombustion-heated reformer 2008 and/or the electrically-heated reformer2010 (e.g., using one or more lines or conduits). The storage tank 2002may provide the incoming ammonia stream 2004 (for example, by actuatinga valve). In some instances, the heat exchanger 2006 may facilitate heattransfer from the (relatively warmer) reformate stream 2020 to the(relatively cooler) incoming ammonia stream 2004 to preheat and/orvaporize the incoming ammonia stream 2004 (changing the phase of theammonia stream 2004 from liquid to gas). The incoming ammonia stream2004 may then enter the reformers 2008 and 2010 to be reformed intohydrogen and nitrogen.

In some embodiments, the incoming ammonia stream 2004 may first bepartially reformed by the electrically-heated reformer 2010 into apartially cracked reformate stream 2020 (e.g., comprising at least about10% H₂/N₂ mixture by molar fraction) (for example, during a start-up orinitiation process). Subsequently, the partially cracked reformatestream 2020 may be further reformed in the combustion-heated reformer2008 to generate a substantially cracked reformate stream (e.g.,comprising less than about 10,000 ppm of residual or trace ammonia byvolume and/or greater than about 99% H₂/N₂ mixture by molar fraction).Passing the ammonia stream 2004 through the electrically-heated reformer2010 first, and then subsequently passing the ammonia stream 2004through the combustion-heated reformer 2008, may advantageously resultin more complete ammonia conversion (e.g., greater than about 99%).

In some embodiments, the incoming ammonia stream 2004 may first bepartially reformed by the combustion-heated reformer 2008 into apartially cracked reformate stream 2020 (e.g., comprising at least about10% H₂/N₂ mixture by molar fraction). Subsequently, the partiallycracked reformate stream 2020 may be further reformed in theelectrically-heated reformer 2010 to generate a substantially crackedreformate stream (e.g., comprising less than about 10,000 ppm ofresidual or trace ammonia by volume and/or greater than about 99% H₂/N₂mixture by molar fraction). Passing the ammonia stream 2004 through thecombustion-heated reformer 2008 first, and then subsequently passing theammonia stream 2004 through the electrically-heated reformer 2010, mayadvantageously result in more complete ammonia conversion (e.g., greaterthan about 99%).

In some cases, the incoming ammonia stream 2004 may first be preheatedby the combustion exhaust 2014 and/or the combustion heater 2009. Insome cases, the preheated incoming ammonia stream 2004 may then enterthe reformers 2008 and 2010 to be reformed into hydrogen and nitrogen.

In some embodiments, the incoming ammonia stream 2004 may first bereformed by the electrically-heated reformer 2010 to generate apartially or substantially cracked reformate stream 2020 (for example,during a start-up or initiation process). Subsequently, at least part ofthe partially or substantially cracked reformate stream 2020 generatedby the electrically-heated reformer 2010 may be combusted as acombustion fuel to heat at least one combustion heater 2009 of the oneor more combustion-heated reformers 2008.

In some cases, the electrically-heated reformer 2010 may be configuredto preheat or vaporize the incoming ammonia stream 2004 (to avoidreforming liquid ammonia). In some cases, the electrically-heatedreformer 2010 may reform or crack the incoming ammonia stream 2004 at anammonia conversion efficiency of at least about 10, 15, 20, 25, 30, 35,40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 99, or 99.5%. In somecases, the electrically-heated reformer 2010 may reform or crack theincoming ammonia stream 2004 at an ammonia conversion efficiency of atmost about 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80,85, 90, 95, 99, or 99.5%. In some cases, the electrically-heatedreformer 2010 may reform or crack the incoming ammonia stream 2004 at anammonia conversion efficiency of about 10 to about 30, about 20 to about40, about 30 to about 50, about 40 to about 60, about 50 to about 70,about 60 to about 80, about 70 to about 90, about 80 to about 99%, orabout 90 to about 99.5%.

In some cases, power input to the electric heater 2011 of theelectrically-heated reformer 2010 may be reduced or entirely turned offbased on a temperature of the combustion-heated reformer 2008 and/or thecombustion heater 2009 being equal to or greater than a targettemperature (e.g., in a target temperature range). In some cases, powerinput to the electric heater 2011 of the electrically-heated reformer2010 may be reduced or entirely turned off based on a flow rate of theincoming ammonia stream 2004 being equal to or greater than a targetflow rate range. In some cases, power input to the electric heater 2011of the electrically-heated reformer 2010 may be turned on or increasedduring an entire operational time period of the ammonia reforming system2000 (e.g., during the startup mode, the operation mode, and/or the hotstandby mode described in the present disclosure). In some cases, powerinput to the electric heater 2011 of the electrically-heated reformer2010 may be turned on or off, or increased intermittently during theoperational time period of the ammonia reforming system 2000 (e.g.,turned on or increased during the startup mode and/or the hot standbymode, and turned off or decreased during the operation mode).

In some cases, power input to the electric heater 2011 may be controlledso that the temperature of the electrically-heated reformer 2010 and/orthe electrical heater 2011 increases or decreases at a targettemperature change rate (ΔTemperature/ΔTime, e.g., ° C./minute). In somecases, the target temperature change rate is at least about 5, 10, 20,25, 30, 35, 40, 45, 50, 60, 65, 70, 75, 80, 85, 90, 95, or 100°C./minute. In some cases, the target temperature change rate is at mostabout 5, 10, 20, 25, 30, 35, 40, 45, 50, 60, 65, 70, 75, 80, 85, 90, 95,or 100° C./minute.

The filtered reformate stream 2023 may be provided to the hydrogenprocessing module 2024 to generate electrical power 2026. An externalload (e.g., an electrical motor to power a transport vehicle, or astationary electrical grid) may utilize the electrical power 2026. Thefuel cell 2024 may provide the anode off-gas 2028 (e.g., containingunconsumed or unconverted hydrogen) to the combustion heater 2009 tocombust for self-heating.

In some embodiments, the ammonia reforming system 2000 includes abattery (so that the system 2000 is a hybrid fuel cell-battery system).The battery may be configured to power an external load in addition tothe hydrogen processing module 2024. The hydrogen processing module 2024may be configured to charge the battery (for example, based a charge ofthe battery being less than a threshold charge).

In some cases, the hydrogen processing module 2024 comprises steel oriron processing, a combustion engine, a combustion turbine, hydrogenstorage, a chemical process, a hydrogen fueling station, and the like.

Reformer Control

In some cases, ammonia may be directed to a reformer at an ammonia flowrate to generate a reformate stream comprising hydrogen and nitrogen.The reformer may include any catalyst described herein. In some cases,the catalyst may be at a temperature greater than 575° C. and less thanabout 725° C., and the reformate stream may be generated at an ammoniaconversion efficiency of greater than about 70% and less than about99.99%.

The first portion of the reformate stream may be combusted with oxygenat an oxygen flow rate in a combustion heater to heat the reformer. Asecond portion of the reformate stream may be processed in a hydrogenprocessing module (e.g., a fuel cell or an internal combustion engine).Based at least in part on a stimulus, at least one of the following maybe performed: (i) changing (increasing or decreasing) the ammonia flowrate to the reformer, (ii) changing (increasing or decreasing) apercentage of the reformate stream that is the first portion of thereformate stream, (iii) changing (increasing or decreasing) a percentageof the reformate stream that is the second portion of the reformatestream, or (iv) changing (increasing or decreasing) the oxygen flowrate.

In some cases, the stimulus comprises a change in an amount of thehydrogen used by the hydrogen processing module (e.g., change inhydrogen demand). In some cases, the stimulus comprises a temperature ofthe reformer being outside of a target temperature range. In some cases,the stimulus comprises a change in an amount or concentration of ammoniain the reformate stream.

In some cases, the stimulus is based at least in part on an increase inan amount of the hydrogen used by the hydrogen processing module. Insome cases, the increase in an amount of hydrogen used is a projectedincrease in an amount of hydrogen used (in other words, a predictedincrease in demand of hydrogen by the hydrogen processing module at asubsequent time) or a target increase in an amount of hydrogen used. Insome cases, based on the increase in an amount of hydrogen used by thehydrogen processing module, one or more of (i) the ammonia flow rate isincreased, (ii) the percentage of the reformate stream that is the firstportion of the reformate stream is decreased, (iii) the percentage ofthe reformate stream that is the second portion of the reformate streamis increased, or (iv) the percentage of the reformate stream that isvented or flared (or directed out of the combustion heater) isdecreased.

In some cases, the stimulus is based at least in part on a decrease inan amount of the hydrogen used by the hydrogen processing module. Insome cases, the decrease in an amount of hydrogen used is a projecteddecrease in an amount of hydrogen used (in other words, a predicteddecrease in demand of hydrogen by the hydrogen processing module at asubsequent time) or a target decrease in an amount of hydrogen used. Insome cases, based on the decrease in an amount of hydrogen used by thehydrogen processing module, one or more of: (i) the ammonia flow rate isdecreased, (ii) the percentage of the reformate stream that is the firstportion of the reformate stream is increased, (iii) the percentage ofthe reformate stream that is the second portion of the reformate streamis decreased, or (iv) the percentage of the reformate stream that isvented or flared (or directed out of the combustion heater) isincreased.

In some cases, the stimulus comprises (a) a discontinued processing ofhydrogen using the hydrogen processing module or (b) a fault ormalfunction of the hydrogen processing module.

In some cases, a plurality of hydrogen processing modules each comprisethe hydrogen processing module, and the stimulus comprises at least oneof (a) a discontinued processing of the hydrogen using one of theplurality of hydrogen processing modules and/or (b) a fault ormalfunction in one of the plurality of hydrogen processing modules.

In some cases, the percentage of the reformate stream that is the secondportion of the reformate stream (processed by the hydrogen processingmodule) is changed to about zero percent in response to the stimulus.

In some cases, substantially none of the reformate stream is directed tothe hydrogen processing module in response to the stimulus.

In some cases, substantially all of the reformate stream is directed toat least one of a combustion-heated reformer and/or a combustion heaterin thermal communication with the combustion-heated reformer in responseto the stimulus.

In some cases, a portion of the reformate stream is vented or flared inresponse to the stimulus.

In some cases, the stimulus is detected using a sensor. In some cases,the stimulus is communicated to a controller. In some cases, theadjustment(s) are performed with the aid of a programmable computer orcontroller. In some cases, the adjustment(s) are performed using a flowcontrol unit.

In some cases, the stimulus is a pressure. In some cases, the pressureis increased in response to decreasing a flow rate to the hydrogenprocessing module. In some cases, the stimulus is a pressure of thereformate stream.

In some cases, a temperature in the reformer or the combustion heatermay be measured, and, based at least in part on the measured at leastone of the following may be performed: (i) changing (increasing ordecreasing) the ammonia flow rate to the reformer, (ii) changing(increasing or decreasing) a percentage of the reformate stream that isthe first portion of the reformate stream, (iii) changing (increasing ordecreasing) a percentage of the reformate stream that is the secondportion of the reformate stream, (iv) changing (increasing ordecreasing) the oxygen flow rate, or (v) changing a percentage of thereformate stream that is directed out of the combustion heater.

In some cases, the second portion of the reformate stream that isprocessed by the hydrogen processing module may not be completelyconsumed or utilized by the hydrogen processing. A leftover stream oroff-gas (comprising at least hydrogen) may be provided from the hydrogenprocessing module to the combustion heater (to combust as fuel).Therefore, increasing or decreasing a percentage of the reformate streamthat is the second portion of the reformate stream may provide more orless fuel to the combustion heater (therefore a percentage of thereformate stream that is the first portion of the reformate stream maybe increased or decreased).

Embodiments

Embodiment 1: A catalyst for ammonia decomposition, comprising: asupport comprising at least one of alumina, silica, carborundum,zeolite, ceria, zirconia, graphite oxide, carbon, graphene, carbonnanofibers and carbon nanotubes, and a layer adjacent to the support,wherein the layer comprises the support material doped with an oxide ofat least one of an alkali metal, an alkaline earth metal, or a rareearth metal; and one or more active metal particles adjacent to thelayer, wherein the one or more active metal particles comprises at leastone of Ru, Ni, Rh, Ir, Co, Fe, Pt, Cr, Mo, Pd, or Cu; and wherein theconcentration of the active metal particles is at least about 0.1, andnot more than about 15 wt %.

Embodiment 2: The catalyst of embodiment 1, wherein the supportcomprises aluminum and oxygen.

Embodiment 3. The catalyst of embodiment 1, wherein the layer comprisesat least one of theta-alumina (θ-alumina) or gamma-alumina (γ-alumina).

Embodiment 4. The catalyst of embodiment 1, wherein the layer comprisesa perovskite phase.

Embodiment 5. The catalyst of embodiment 1, wherein the layer comprisesLa at a concentration of at least about 0.1, and not more than about 50mol %.

Embodiment 6. The catalyst of embodiment 1, wherein said layer comprisesLa and Ce, wherein the molar ratio of the La to the Ce is at least about10:90, and not more than about 90:10.

Embodiment 7. The catalyst of embodiment 1, wherein at least one of thesupport or the layer further comprises a promoter comprising at leastone of K, Cs, or Rb.

Embodiment 8. The catalyst of embodiment 7, wherein a molar ratio of thepromoter to the active metal particles is at least about 1:2, and notmore than about 10:1.

Embodiment 9. The catalyst of embodiment 1, wherein the active metalparticles comprise ruthenium (Ru).

Embodiment 10. The catalyst of embodiment 9, wherein the concentrationof Ru is at least about 0.5, and not more than about 10 wt %.

Embodiment 11. The catalyst of embodiment 9, wherein the layer comprisesnanoparticles of elemental Ru.

Embodiment 12. The catalyst of embodiment 1, wherein the layer comprisesoxide nanoparticles of at least one of La, Ce, K, Cs or Rb.

Embodiment 13. The catalyst of embodiment 1, wherein the layer comprisesannealed nanoparticles of at least one of La, Ce, K, Cs or Rb.

Embodiment 14. A method of producing a catalyst for ammoniadecomposition, comprising: (a) providing a support comprising at leastone of alumina, silica, carborundum, zeolite, ceria, zirconia, graphiteoxide, carbon, graphene, carbon nanofibers, or carbon nanotubes orprecursor(s) thereof; (b) depositing a layer adjacent to the supportcomprising at least one of an alkali metal oxide or precursors thereof,an alkaline earth metal oxide or precursors thereof, or a rare earthmetal oxide or precursor(s) thereof, to form a doped support; (c)depositing a precursor of one or more active metal particles adjacent tothe layer, wherein the one or more active metal particles comprise atleast one of Ru, Ni, Rh, Ir, Co, Fe, Pt, Cr, Mo, Pd, or Cu, wherein theconcentration of the active metal particles is at least about 0.1 wt %and not more than about 15 wt %; and (d) maintaining the doped supportat a temperature of at least about 200° C. and not more than about 1300°C. for a duration of at least about 0.1 hour and not more than about 168hours in an atmosphere comprising hydrogen.

Embodiment 15. The method of embodiment 14, wherein (b) furthercomprises: maintaining the doped support at a temperature of at leastabout 20° C. and not more than about 150° C., for a duration of at leastabout 0.1 hour and not more than about 168 hours in vacuo, or in aninert, anoxic or non-oxidizing atmosphere below 5 bar absolute pressure.

Embodiment 16. The method of embodiment 14, wherein (b) furthercomprises maintaining the doped support at a temperature of at leastabout 300° C. and not more than about 1300° C. for a duration of atleast about 0.1 hour and not more than about 168 hours, in anon-reducing atmosphere, comprising at least one of: air, N₂, CO₂, Ar,He, Kr, or Xe.

Embodiment 17. The method of embodiment 14, wherein (b) furthercomprises maintaining the doped support at a temperature of at leastabout 300° C. and not more than about 1300° C. for a duration of atleast about 0.1 hour and not more than about 168 hours, in an inert,anoxic or non-oxidizing atmosphere, comprising at least one of: N₂, H₂,Ar, NH₃, CO, CO₂, He, Kr, or Xe.

Embodiment 18. The method of embodiment 14, wherein the supportcomprises aluminum and oxygen.

Embodiment 19. The method of embodiment 14, wherein the layer comprisesat least one of theta alumina (θ-alumina) or gamma alumina (γ-alumina).

Embodiment 20. The method of embodiment 14, wherein the layer comprisesa perovskite phase.

Embodiment 21. The method of embodiment 14, wherein the layer comprisesLa at a concentration of at least about 0.1 and not more than about 50mol %.

Embodiment 22. The method of embodiment 14, wherein the layer comprisesLa and Ce, wherein a molar ratio of the La to the Ce is at least about10:90 and not more than about 90:10.

Embodiment 23. The method of embodiment 14, wherein the layer comprisesdepositing one or more promoters or promoter precursor(s); wherein theone or more promoters or promoter precursor(s) comprise at least one ofK, Cs, or Rb.

Embodiment 24. The method of embodiment 23, wherein the layer furthercomprises a molar ratio of the one or more promoters or promoterprecursor(s) to the one or more active metal particles comprising atleast about 1:2 and not more than about 10:1.

Embodiment 25. The method of embodiment 14, wherein the one or moreactive metal particles further comprise ruthenium (Ru).

Embodiment 26. The method of embodiment 25, wherein a concentration ofRu comprises at least about 0.5 wt % and not more than about 10 wt %.

Embodiment 27. The method of embodiment 25, wherein (c) the precursor ofthe one or more active metal particles comprises at least one ofRu(NO)(NO₃)₃, Ru(NO₃)₃, RuCl₃, Ru₃(CO)₁₂, Ru(NH₃)₆Cl₃ (ruthenium(III)chloride hexaammoniate), (CHD)Ru(CO)₃ (cyclohexadiene rutheniumtricarbonyl), (BD)Ru(CO)₃ (butadiene ruthenium tricarbonyl), or(DMBD)Ru(CO)₃ (dimethylbutadiene ruthenium tricarbonyl).

Embodiment 28. The method of embodiment 14, wherein (a) the support orprecursor(s) thereof comprise beads or pellets; wherein the beads or thepellets comprise at least one of (i) a diameter of at least about 0.1 mmand not more than about 10 mm, or (ii) a surface area per unit mass ofat least about 50 m²/g and not more than about 500 m²/g.

Embodiment 29. A method of ammonia decomposition comprising: (a)providing a catalyst, comprising: a support comprising at least one ofalumina, silica, carborundum, zeolite, ceria, zirconia, graphite oxide,carbon, graphene, carbon nanofibers and carbon nanotubes, and a layeradjacent to the support, wherein the layer comprises the supportmaterial doped with an oxide of at least one of an alkali metal, analkaline earth metal and a rare earth metal; and one or more activemetal particles adjacent to the layer, wherein the one or more activemetal particles comprise at least one of Ru, Ni, Rh, Jr, Co, Fe, Pt, Cr,Mo, Pd, or Cu; and wherein the concentration of the active metalparticles is at least about 0.1, and not more than about 15 wt %; and(b) bringing the catalyst in contact with ammonia at a temperature of atleast about 400° C. and not more than about 700° C. to generate hydrogenand nitrogen at an ammonia conversion efficiency of at least 70%.

Embodiment 30. The method of embodiment 29, wherein the ammonia iscontacted on the catalyst at a space velocity of at least about 1 andnot more than about 30 liters per hour per gram of catalyst, at atemperature of at least about 400° C. and not more than about 700° C.

Embodiment 31. The method of embodiment 29, further comprisinggenerating electricity by providing hydrogen produced by the catalyst toat least one fuel cell, wherein the at least one fuel cell comprises aProton Exchange Membrane Fuel Cell (PEMFC), a Solid Oxide Fuel Cell(SOFC), a Molten Carbonate Fuel Cell (MCFC), an Alkaline Fuel Cell(AFC), an Alkaline Membrane Fuel Cell (AMFC), or a Phosphoric Acid FuelCell (PAFC).

Embodiment 32. The method of embodiment 29, further comprisinggenerating power or electricity by providing hydrogen produced by thecatalyst to one or more combustion engines or turbines.

Embodiment 33. A system configured to reform ammonia using the method ofembodiment 29.

Embodiment 34. A catalyst for ammonia decomposition, comprising: asupport comprising at least one of alumina, silica, carborundum,zeolite, ceria, zirconia, graphite oxide, carbon, graphene, carbonnanofibers and carbon nanotubes, and a layer adjacent to the support,wherein the layer comprises the support material doped with an oxide ofat least one of an alkali metal, an alkaline earth metal, or a rareearth metal; and one or more active metal particles adjacent to thelayer, wherein the one or more active metal particles comprises at leastone of Ru, Ni, Rh, Ir, Co, Fe, Pt, Cr, Mo, Pd, or Cu; and wherein theconcentration of the active metal particles is at least about 0.1, andnot more than about 15 wt %.

Embodiment 35. The catalyst of embodiment 34, wherein the supportcomprises aluminum and oxygen.

Embodiment 36. The catalyst of embodiment 34, wherein the layercomprises at least one of theta-alumina (θ-alumina) or gamma-alumina(γ-alumina).

Embodiment 37. The catalyst of embodiment 34, wherein the layercomprises a perovskite phase.

Embodiment 38. The catalyst of embodiment 34, wherein the layercomprises La at a concentration of at least about 0.1, and not more thanabout 50 mol %.

Embodiment 39. The catalyst of embodiment 34, wherein said layercomprises La and Ce, wherein the molar ratio of the La to the Ce is atleast about 10:90, and not more than about 90:10.

Embodiment 40. The catalyst of embodiment 34, wherein at least one ofthe support or the layer further comprises a promoter comprising atleast one of K, Cs, or Rb.

Embodiment 41. The catalyst of embodiment 40, wherein a molar ratio ofthe promoter to the active metal particles is at least about 1:2, andnot more than about 10:1.

Embodiment 42. The catalyst of embodiment 34, wherein the active metalparticles comprise ruthenium (Ru).

Embodiment 43. The catalyst of embodiment 42, wherein the concentrationof Ru is at least about 0.5, and not more than about 10 wt %.

Embodiment 44. The catalyst of embodiment 42, wherein the layercomprises nanoparticles of elemental Ru.

Embodiment 45. The catalyst of embodiment 34, wherein the layercomprises oxide nanoparticles of at least one of La, Ce, K, Cs or Rb.

Embodiment 46. The catalyst of embodiment 34, wherein the layercomprises annealed nanoparticles of at least one of La, Ce, K, Cs or Rb.

Embodiment 47. A method of producing a catalyst for ammoniadecomposition, comprising: (a) providing a support comprising at leastone of alumina, silica, carborundum, zeolite, ceria, zirconia, graphiteoxide, carbon, graphene, carbon nanofibers, or carbon nanotubes orprecursor(s) thereof; (b) depositing a layer adjacent to the supportcomprising at least one of an alkali metal oxide or precursors thereof,an alkaline earth metal oxide or precursors thereof, or a rare earthmetal oxide or precursor(s) thereof, to form a doped support; (c)depositing a precursor of one or more active metal particles adjacent tothe layer, wherein the one or more active metal particles comprise atleast one of Ru, Ni, Rh, Ir, Co, Fe, Pt, Cr, Mo, Pd, or Cu, wherein theconcentration of the active metal particles is at least about 0.1 wt %and not more than about 15 wt %; and (d) maintaining the doped supportat a temperature of at least about 200° C. and not more than about 1300°C. for a duration of at least about 0.1 hour and not more than about 168hours in an atmosphere comprising hydrogen.

Embodiment 48. The method of embodiment 47, wherein (b) furthercomprises: maintaining the doped support at a temperature of at leastabout 20° C. and not more than about 150° C., for a duration of at leastabout 0.1 hour and not more than about 168 hours in vacuo, or in aninert, anoxic or non-oxidizing atmosphere below 5 bar absolute pressure.

Embodiment 49. The method of embodiment 47, wherein (b) furthercomprises maintaining the doped support at a temperature of at leastabout 300° C. and not more than about 1300° C. for a duration of atleast about 0.1 hour and not more than about 168 hours, in anon-reducing atmosphere, comprising at least one of: air, N₂, CO₂, Ar,He, Kr, or Xe.

Embodiment 50. The method of embodiment 47, wherein (b) furthercomprises maintaining the doped support at a temperature of at leastabout 300° C. and not more than about 1300° C. for a duration of atleast about 0.1 hour and not more than about 168 hours, in an inert,anoxic or non-oxidizing atmosphere, comprising at least one of: N₂, H₂,Ar, NH₃, CO, CO₂, He, Kr, or Xe.

Embodiment 51. The method of embodiment 47, wherein the supportcomprises aluminum and oxygen.

Embodiment 52. The method of embodiment 14, wherein the layer comprisesat least one of theta alumina (θ-alumina) or gamma alumina (γ-alumina).

Embodiment 53. The method of embodiment 47, wherein the layer comprisesa perovskite phase.

Embodiment 54. The method of embodiment 47, wherein the layer comprisesLa at a concentration of at least about 0.1 and not more than about 50mol %.

Embodiment 55. The method of embodiment 47, wherein the layer comprisesLa and Ce, wherein a molar ratio of the La to the Ce is at least about10:90 and not more than about 90:10.

Embodiment 56. The method of embodiment 47, wherein the layer comprisesdepositing one or more promoters or promoter precursor(s); wherein theone or more promoters or promoter precursor(s) comprise at least one ofK, Cs, or Rb.

Embodiment 57. The method of embodiment 56, wherein the layer furthercomprises a molar ratio of the one or more promoters or promoterprecursor(s) to the one or more active metal particles comprising atleast about 1:2 and not more than about 10:1.

Embodiment 58. The method of embodiment 47, wherein the one or moreactive metal particles further comprise ruthenium (Ru).

Embodiment 59. The method of embodiment 58, wherein a concentration ofRu comprises at least about 0.5 wt % and not more than about 10 wt %.

Embodiment 60. The method of embodiment 58, wherein (c) the precursor ofthe one or more active metal particles comprises at least one ofRu(NO)(NO₃)₃, Ru(NO₃)₃, RuCl₃, Ru₃(CO)₁₂, Ru(NH₃)₆Cl₃ (ruthenium(III)chloride hexaammoniate), (CHD)Ru(CO)₃ (cyclohexadiene rutheniumtricarbonyl), (BD)Ru(CO)₃ (butadiene ruthenium tricarbonyl), or(DMBD)Ru(CO)₃ (dimethylbutadiene ruthenium tricarbonyl).

Embodiment 61. The method of embodiment 47, wherein (a) the support orprecursor(s) thereof comprise beads or pellets; wherein the beads or thepellets comprise at least one of (i) a diameter of at least about 0.1 mmand not more than about 10 mm, or (ii) a surface area per unit mass ofat least about 50 m²/g and not more than about 500 m²/g.

Embodiment 62. A method of ammonia decomposition comprising: (a)providing a catalyst, comprising: a support comprising at least one ofalumina, silica, carborundum, zeolite, ceria, zirconia, graphite oxide,carbon, graphene, carbon nanofibers and carbon nanotubes, and a layeradjacent to the support, wherein the layer comprises the supportmaterial doped with an oxide of at least one of an alkali metal, analkaline earth metal and a rare earth metal; and one or more activemetal particles adjacent to the layer, wherein the one or more activemetal particles comprise at least one of Ru, Ni, Rh, Jr, Co, Fe, Pt, Cr,Mo, Pd, or Cu; and wherein the concentration of the active metalparticles is at least about 0.1, and not more than about 15 wt %; and(b) bringing the catalyst in contact with ammonia at a temperature of atleast about 400° C. and not more than about 700° C. to generate areformate stream comprising hydrogen and nitrogen at an ammoniaconversion efficiency of at least about 70% and at most about 99.9%.

Embodiment 63. The method of embodiment 62, wherein the ammonia iscontacted on the catalyst at a space velocity of at least about 1 andnot more than about 100 liters of ammonia per hour per gram of catalyst.

Embodiment 64. The method of embodiment 62, further comprisinggenerating electricity by providing hydrogen produced by the catalyst toat least one fuel cell, wherein the at least one fuel cell comprises aProton Exchange Membrane Fuel Cell (PEMFC), a Solid Oxide Fuel Cell(SOFC), a Molten Carbonate Fuel Cell (MCFC), an Alkaline Fuel Cell(AFC), an Alkaline Membrane Fuel Cell (AMFC), or a Phosphoric Acid FuelCell (PAFC).

Embodiment 65. The method of embodiment 62, further comprisinggenerating power or electricity by providing hydrogen produced by thecatalyst to one or more combustion engines or turbines.

Embodiment 66. A system configured to reform ammonia using the method ofembodiment 62.

Embodiment 67. The method of embodiment 62, wherein contacting thecatalyst with ammonia to generate the reformate stream is anauto-thermal reforming process so that at least part of the reformatestream provides heat for the auto-thermal reforming process.

Embodiment 68. The method of embodiment 67, wherein the at least part ofthe reformate stream is at least one of: (1) combusted to generate theheat, or (2) converted by hydrogen-to-electricity conversion to generatethe heat, thereby providing the heat for the auto-thermal reformingprocess.

Embodiment 69. The method of embodiment 62, wherein undecomposed ammoniain the reformate stream is removed by an ammonia filter.

Embodiment 70. The method of embodiment 69, wherein the ammonia filtercomprises at least one of an adsorbent, a membrane separation module, oran ammonia scrubber.

Embodiment 71. The method of embodiment 62, wherein a pressure swingadsorption (PSA) module is used to remove nitrogen from the reformatestream.

Embodiment 72. The method of embodiment 62, wherein (b) comprisesdirecting the ammonia to a first reformer to generate the reformatestream; wherein the method comprises combusting the reformate stream ina combustion heater to heat a second reformer; and directing additionalammonia to the second reformer to generate additional hydrogen for thereformate stream, wherein a first portion of the reformate stream iscombusted to heat the second reformer.

Embodiment 73. The method of embodiment 72, wherein the first reformeris heated using at least one of an electrical heater or combustion ofthe reformate stream.

Embodiment 74. The method of embodiment 62, wherein (b) comprisesdirecting the ammonia to a reformer at an ammonia flow rate to generatethe reformate stream, wherein the method further comprises: combusting afirst portion of the reformate stream with oxygen at an oxygen flow ratein a combustion heater to heat the reformer; processing a second portionof the reformate stream in a hydrogen processing module; and based atleast in part on a stimulus, performing one or more of: i. changing theammonia flow rate; ii. changing a percentage of the reformate streamthat is the first portion of the reformate stream; iii. changing apercentage of the reformate stream that is the second portion of thereformate stream; or iv. changing the oxygen flow rate.

Embodiment 75. The method of embodiment 62, wherein (b) comprisesdirecting the ammonia to a reformer at an ammonia flow rate to generatethe reformate stream, wherein the method further comprises: combusting afirst portion of the reformate stream with oxygen at an oxygen flow ratein a combustion heater to heat the reformer; processing a second portionof the reformate stream in a hydrogen processing module; measuring atemperature in the reformer or the combustion heater; and based at leastin part on the measured temperature being outside of a targettemperature range of the reformer or the combustion heater, performingone or more of: i. changing the ammonia flow rate; ii. changing theoxygen flow rate; iii. changing a percentage of the reformate streamthat is the second portion of the reformate stream; iv. changing apercentage of the reformate stream that is the first portion of thereformate stream; or v. changing a percentage of the reformate streamthat is directed out of the combustion heater.

While preferred embodiments of the present invention have been shown anddescribed herein, it will be obvious to those skilled in the art thatsuch embodiments are provided by way of example only. It is not intendedthat the invention be limited by the specific examples provided withinthe specification. While the invention has been described with referenceto the aforementioned specification, the descriptions and illustrationsof the embodiments herein are not meant to be construed in a limitingsense. Numerous variations, changes, and substitutions will now occur tothose skilled in the art without departing from the invention.Furthermore, it shall be understood that all aspects of the inventionare not limited to the specific depictions, configurations or relativeproportions set forth herein which depend upon a variety of conditionsand variables. It should be understood that various alternatives to theembodiments of the invention described herein may be employed inpracticing the invention. It is therefore contemplated that theinvention shall also cover any such alternatives, modifications,variations or equivalents. It is intended that the following claimsdefine the scope of the invention and that systems, methods andstructures within the scope of these claims and their equivalents becovered thereby.

What is claimed is:
 1. A method of ammonia decomposition comprising: (a)providing a catalyst, comprising: a support comprising alumina and alayer adjacent to the support, wherein the layer comprises the supportdoped with an oxide of at least one of an alkali metal and a rare earthmetal; wherein the layer comprises aluminum (Al), cerium (Ce), andlanthanum (La), wherein a molar ratio of La and Ce comprises at leastabout 50:50 and not more than about 90:10; and one or more active metalsadjacent to the layer, wherein the one or more active metals compriseRu, Pt, or Pd; wherein a concentration of the one or more active metalsis at least about 0.1, and not more than about 15 wt %; and (b) bringingthe catalyst in contact with ammonia at a temperature of at least about400° C. and not more than about 700° C. to generate a reformate streamcomprising hydrogen and nitrogen at an ammonia conversion efficiency ofat least about 70% and at most about 99.9%.
 2. The method of claim 1,wherein the layer comprises theta alumina (θ-alumina) or gamma alumina(γ-alumina).
 3. The method of claim 1, wherein the layer comprises La ata concentration of at least about 1 and not more than about 20 mol %with respect to the layer and support.
 4. The method of claim 1, whereinthe alkali metal is K or Cs, and the layer comprises a molar ratio of Kor Cs to the one or more active metals comprising at least about 1:2 andnot more than about 6:1.
 5. The method of claim 1, wherein the one ormore active metals is Ru, and a concentration of the Ru comprises atleast about 0.5 wt % and not more than about 5 wt % with respect to aweight of the catalyst.
 6. The method of claim 1, wherein the ammonia isbrought in contact with the catalyst at a space velocity of at leastabout 1 and not more than about 100 liters of ammonia per hour per gramof catalyst.
 7. The method of claim 1, further comprising generatingelectricity by providing hydrogen produced by the catalyst to at leastone fuel cell, wherein the at least one fuel cell comprises a ProtonExchange Membrane Fuel Cell (PEMFC), a Solid Oxide Fuel Cell (SOFC), aMolten Carbonate Fuel Cell (MCFC), an Alkaline Fuel Cell (AFC), anAlkaline Membrane Fuel Cell (AMFC), or a Phosphoric Acid Fuel Cell(PAFC).
 8. The method of claim 1, wherein contacting the catalyst withammonia to generate the reformate stream is an auto-thermal reformingprocess so that at least part of the reformate stream provides heat forthe auto-thermal reforming process.
 9. The method of claim 8, whereinthe at least part of the reformate stream is at least one of: (1)combusted to generate the heat, or (2) converted byhydrogen-to-electricity conversion to generate the heat, therebyproviding the heat for the auto-thermal reforming process.
 10. Themethod of claim 1, wherein undecomposed ammonia in the reformate streamis removed by an ammonia filter, wherein the ammonia filter comprises anadsorbent, a membrane separation module, or an ammonia scrubber.
 11. Themethod of claim 1, wherein a pressure swing adsorption (PSA) module isused to remove nitrogen from the reformate stream.
 12. The method ofclaim 1, wherein (b) comprises directing the ammonia to a first reformerto generate the reformate stream; wherein the method comprisescombusting the reformate stream in a combustion heater to heat a secondreformer; and directing additional ammonia to the second reformer togenerate additional hydrogen for the reformate stream, wherein a firstportion of the reformate stream is combusted to heat the secondreformer.
 13. The method of claim 1, wherein (b) comprises directing theammonia to a reformer at an ammonia flow rate to generate the reformatestream, wherein the method further comprises: combusting a first portionof the reformate stream with oxygen at an oxygen flow rate in acombustion heater to heat the reformer; and processing a second portionof the reformate stream in a hydrogen processing module; and based atleast in part on a stimulus, performing one or more of: i. changing theammonia flow rate; ii. changing a percentage of the reformate streamthat is the first portion of the reformate stream; iii. changing apercentage of the reformate stream that is the second portion of thereformate stream; or iv. changing the oxygen flow rate.
 14. The methodof claim 1, wherein (b) comprises directing the ammonia to a reformer atan ammonia flow rate to generate the reformate stream, wherein themethod further comprises: combusting a first portion of the reformatestream with oxygen at an oxygen flow rate in a combustion heater to heatthe reformer; processing a second portion of the reformate stream in ahydrogen processing module; measuring a temperature in the reformer orthe combustion heater; and based at least in part on the measuredtemperature being outside of a target temperature range of the reformeror the combustion heater, performing one or more of: i. changing theammonia flow rate; ii. changing the oxygen flow rate; iii. changing apercentage of the reformate stream that is the second portion of thereformate stream; iv. changing a percentage of the reformate stream thatis the first portion of the reformate stream; or v. changing apercentage of the reformate stream that is directed out of thecombustion heater.
 15. A method of ammonia decomposition comprising: (a)providing a catalyst, comprising: a support comprising alumina and alayer adjacent to the support, wherein the layer comprises the supportdoped with an oxide of at least one of an alkali metal and a rare earthmetal; wherein the layer comprises aluminum (Al), cerium (Ce), andlanthanum (La), wherein the alkali metal is K or Cs; and one or moreactive metals adjacent to the layer, wherein the one or more activemetals comprise Ru, Pt, or Pd; wherein the layer comprises a molar ratioof K or Cs to the one or more active metals comprising at least about1:2 and not more than about 6:1; wherein the concentration of the one ormore active metals is at least about 0.1, and not more than about 15 wt%; and (b) bringing the catalyst in contact with ammonia at atemperature of at least about 400° C. and not more than about 700° C. togenerate a reformate stream comprising hydrogen and nitrogen at anammonia conversion efficiency of at least about 70% and at most about99.9%.
 16. The method of claim 15, wherein the layer comprises thetaalumina (θ-alumina) or gamma alumina (γ-alumina).
 17. The method ofclaim 15, wherein the layer comprises La at a concentration of at leastabout 1 and not more than about 20 mol % with respect to the layer andsupport.
 18. The method of claim 15, wherein a molar ratio of La and Cecomprises at least about 50:50 and not more than about 90:10.
 19. Themethod of claim 15, wherein the one or more active metals is Ru, and aconcentration of the Ru comprises at least about 0.5 wt % and not morethan about 5 wt % with respect to a weight of the catalyst.
 20. Themethod of claim 15, wherein the ammonia is brought in contact with thecatalyst at a space velocity of at least about 1 and not more than about100 liters of ammonia per hour per gram of catalyst.
 21. The method ofclaim 15, further comprising generating electricity by providinghydrogen produced by the catalyst to at least one fuel cell, wherein theat least one fuel cell comprises a Proton Exchange Membrane Fuel Cell(PEMFC), a Solid Oxide Fuel Cell (SOFC), a Molten Carbonate Fuel Cell(MCFC), an Alkaline Fuel Cell (AFC), an Alkaline Membrane Fuel Cell(AMFC), or a Phosphoric Acid Fuel Cell (PAFC).
 22. The method of claim15, wherein contacting the catalyst with ammonia to generate thereformate stream is an auto-thermal reforming process so that at leastpart of the reformate stream provides heat for the auto-thermalreforming process.
 23. The method of claim 22, wherein the at least partof the reformate stream is at least one of: (1) combusted to generatethe heat, or (2) converted by hydrogen-to-electricity conversion togenerate the heat, thereby providing the heat for the auto-thermalreforming process.
 24. The method of claim 15, wherein undecomposedammonia in the reformate stream is removed by an ammonia filter, whereinthe ammonia filter comprises an adsorbent, a membrane separation module,or an ammonia scrubber.
 25. The method of claim 15, wherein a pressureswing adsorption (PSA) module is used to remove nitrogen from thereformate stream.
 26. The method of claim 15, wherein (b) comprisesdirecting the ammonia to a first reformer to generate the reformatestream; wherein the method comprises combusting the reformate stream ina combustion heater to heat a second reformer; and directing additionalammonia to the second reformer to generate additional hydrogen for thereformate stream, wherein a first portion of the reformate stream iscombusted to heat the second reformer.
 27. The method of claim 15,wherein (b) comprises directing the ammonia to a reformer at an ammoniaflow rate to generate the reformate stream, wherein the method furthercomprises: combusting a first portion of the reformate stream withoxygen at an oxygen flow rate in a combustion heater to heat thereformer; and processing a second portion of the reformate stream in ahydrogen processing module; and based at least in part on a stimulus,performing one or more of: i. changing the ammonia flow rate; ii.changing a percentage of the reformate stream that is the first portionof the reformate stream; iii. changing a percentage of the reformatestream that is the second portion of the reformate stream; or iv.changing the oxygen flow rate.
 28. The method of claim 15, wherein (b)comprises directing the ammonia to a reformer at an ammonia flow rate togenerate the reformate stream, wherein the method further comprises:combusting a first portion of the reformate stream with oxygen at anoxygen flow rate in a combustion heater to heat the reformer; processinga second portion of the reformate stream in a hydrogen processingmodule; measuring a temperature in the reformer or the combustionheater; and based at least in part on the measured temperature beingoutside of a target temperature range of the reformer or the combustionheater, performing one or more of: i. changing the ammonia flow rate;ii. changing the oxygen flow rate; iii. changing a percentage of thereformate stream that is the second portion of the reformate stream; iv.changing a percentage of the reformate stream that is the first portionof the reformate stream; or v. changing a percentage of the reformatestream that is directed out of the combustion heater.
 29. A method ofammonia decomposition comprising: (a) providing a catalyst, comprising:a support comprising alumina and a layer adjacent to the support,wherein the layer comprises the support doped with an oxide of at leastone of an alkali metal and a rare earth metal; wherein the layercomprises aluminum (Al), cerium (Ce), and lanthanum (La); and one ormore active metals adjacent to the layer, wherein the one or more activemetals comprise Ru, Pt, or Pd; wherein a concentration of the one ormore active metals is at least about 0.1, and not more than about 15 wt%; and (b) bringing the catalyst in contact with ammonia at atemperature of at least about 400° C. and not more than about 700° C. togenerate a reformate stream comprising hydrogen and nitrogen at anammonia conversion efficiency of at least about 70% and at most about99.9%, wherein the ammonia is brought in contact with the catalyst at aspace velocity of at least about 1 and not more than about 100 liters ofammonia per hour per gram of catalyst.
 30. The method of claim 29,wherein the layer comprises theta alumina (θ-alumina) or gamma alumina(γ-alumina).
 31. The method of claim 29, wherein the layer comprises Laat a concentration of at least about 1 and not more than about 20 mol %with respect to the layer and support.
 32. The method of claim 29,wherein a molar ratio of La and Ce comprises at least about 50:50 andnot more than about 90:10.
 33. The method of claim 29, wherein thealkali metal is K or Cs, and the layer comprises a molar ratio of K orCs to the one or more active metals comprising at least about 1:2 andnot more than about 6:1.
 34. The method of claim 29, wherein the one ormore active metals is Ru, and a concentration of the Ru comprises atleast about 0.5 wt % and not more than about 5 wt % with respect to theweight of the catalyst.
 35. The method of claim 29, further comprisinggenerating electricity by providing hydrogen produced by the catalyst toat least one fuel cell, wherein the at least one fuel cell comprises aProton Exchange Membrane Fuel Cell (PEMFC), a Solid Oxide Fuel Cell(SOFC), a Molten Carbonate Fuel Cell (MCFC), an Alkaline Fuel Cell(AFC), an Alkaline Membrane Fuel Cell (AMFC), or a Phosphoric Acid FuelCell (PAFC).
 36. The method of claim 29, wherein contacting the catalystwith ammonia to generate the reformate stream is an auto-thermalreforming process so that at least part of the reformate stream providesheat for the auto-thermal reforming process.
 37. The method of claim 36,wherein the at least part of the reformate stream is at least one of:(1) combusted to generate the heat, or (2) converted byhydrogen-to-electricity conversion to generate the heat, therebyproviding the heat for the auto-thermal reforming process.
 38. Themethod of claim 29, wherein undecomposed ammonia in the reformate streamis removed by an ammonia filter, wherein the ammonia filter comprises anadsorbent, a membrane separation module, or an ammonia scrubber.
 39. Themethod of claim 29, wherein a pressure swing adsorption (PSA) module isused to remove nitrogen from the reformate stream.
 40. The method ofclaim 29, wherein (b) comprises directing the ammonia to a firstreformer to generate the reformate stream; wherein the method comprisescombusting the reformate stream in a combustion heater to heat a secondreformer; and directing additional ammonia to the second reformer togenerate additional hydrogen for the reformate stream, wherein a firstportion of the reformate stream is combusted to heat the secondreformer.
 41. The method of claim 29, wherein (b) comprises directingthe ammonia to a reformer at an ammonia flow rate to generate thereformate stream, wherein the method further comprises: combusting afirst portion of the reformate stream with oxygen at an oxygen flow ratein a combustion heater to heat the reformer; and processing a secondportion of the reformate stream in a hydrogen processing module; andbased at least in part on a stimulus, performing one or more of: v.changing the ammonia flow rate; ii. changing a percentage of thereformate stream that is the first portion of the reformate stream; iii.changing a percentage of the reformate stream that is the second portionof the reformate stream; or iv. changing the oxygen flow rate.
 42. Themethod of claim 29, wherein (b) comprises directing the ammonia to areformer at an ammonia flow rate to generate the reformate stream,wherein the method further comprises: combusting a first portion of thereformate stream with oxygen at an oxygen flow rate in a combustionheater to heat the reformer; processing a second portion of thereformate stream in a hydrogen processing module; measuring atemperature in the reformer or the combustion heater; and based at leastin part on the measured temperature being outside of a targettemperature range of the reformer or the combustion heater, performingone or more of: v. changing the ammonia flow rate; ii. changing theoxygen flow rate; iii. changing a percentage of the reformate streamthat is the second portion of the reformate stream; iv. changing apercentage of the reformate stream that is the first portion of thereformate stream; or v. changing a percentage of the reformate streamthat is directed out of the combustion heater.
 43. A method of ammoniadecomposition comprising: (a) providing a catalyst, comprising: asupport comprising alumina and a layer adjacent to the support, whereinthe layer comprises the support doped with an oxide of at least one ofan alkali metal and a rare earth metal; wherein the layer comprisesaluminum (Al), cerium (Ce), and lanthanum (La); and one or more activemetals adjacent to the layer, wherein the one or more active metalscomprise Ru, Pt, or Pd; wherein a concentration of the one or moreactive metals is at least about 0.1, and not more than about 15 wt %;and (b) bringing the catalyst in contact with ammonia at a temperatureof at least about 400° C. and not more than about 700° C. to generate areformate stream comprising hydrogen and nitrogen at an ammoniaconversion efficiency of at least about 70% and at most about 99.9%,wherein (b) comprises directing the ammonia to a first reformer togenerate the reformate stream; wherein the method comprises combustingthe reformate stream in a combustion heater to heat a second reformer;and directing additional ammonia to the second reformer to generateadditional hydrogen for the reformate stream, wherein a first portion ofthe reformate stream is combusted to heat the second reformer.
 44. Themethod of claim 43, wherein the first reformer is heated using at leastone of an electrical heater or combustion of the reformate stream.
 45. Amethod of ammonia decomposition comprising: (a) providing a catalyst,comprising: a support comprising alumina and a layer adjacent to thesupport, wherein the layer comprises the support material doped with anoxide of at least one of an alkali metal and a rare earth metal; whereinthe layer comprises aluminum (Al), cerium (Ce), and lanthanum (La); andone or more active metals adjacent to the layer, wherein the one or moreactive metals comprise Ru, Pt, or Pd; wherein the concentration of theone or more active metals is at least about 0.1, and not more than about15 wt %; and (b) bringing the catalyst in contact with ammonia at atemperature of at least about 400° C. and not more than about 700° C. togenerate a reformate stream comprising hydrogen and nitrogen at anammonia conversion efficiency of at least about 70% and at most about99.9%, wherein (b) comprises directing the ammonia to a reformer at anammonia flow rate to generate the reformate stream, wherein the methodfurther comprises: combusting a first portion of the reformate streamwith oxygen at an oxygen flow rate in a combustion heater to heat thereformer; and processing a second portion of the reformate stream in ahydrogen processing module; and based at least in part on a stimulus,performing one or more of: i. changing the ammonia flow rate; ii.changing a percentage of the reformate stream that is the first portionof the reformate stream; iii. changing a percentage of the reformatestream that is the second portion of the reformate stream; or iv.changing the oxygen flow rate.
 46. The method of claim 45, wherein thestimulus comprises: x. a change in an amount of the hydrogen used by thehydrogen processing module; y. a temperature of the reformer beingoutside of a target temperature range; or z. a change in an amount orconcentration of ammonia in the reformate stream.
 47. The method ofclaim 46, wherein the change in an amount of the hydrogen used by thehydrogen processing module is a projected change in the amount of thehydrogen used by the hydrogen processing module.
 48. The method of claim45, wherein the hydrogen processing module comprises a fuel cell and thefuel cell provides an anode off-gas comprising hydrogen to thecombustion heater.